Hello and welcome to /r/vnsuggest!

So, you want to start reading Visual Novels but don't know where to start? I got you covered!

First of all, you have to set your system locale to Japanese. It is necessary to run most VNs on your PC. Fuwanovel has a simple guide for Windows systems.

If you want to jump in immediately now, please refer to one of our Recommendation Charts (2012, 2013), or the official recommendation chart from our parent-sub /r/visualnovels. Most VNs there are beginner-friendly.

Make sure to check the VNDB pages of the VNs you're planning to read.

Haven't read any VN before?

• Katawa Shoujo is probably one of the best starter VNs out there. It is free, has a good introduction to the flag-system, and quite an unusual setting.
  Medium length (10-30h) - Age: all-ages with optional 18+ scenes

  Hisao Nakai is a normal high school student, currently in his final year of high school. One day Hisao receives a letter from parties unknown in his locker and waits at the written place for the sender. The person who wrote the letter turns out to be his crush; while speaking to her, he suddenly collapses. He awakes in a hospital bed, and is told by the doctors that the reason he collapsed is due to arrhythmia, a rare heart condition that causes his heartbeat to sometimes become irregular. Due to this, his parents have enrolled him in Yamaku, a school for disabled students of all kinds.

• Narcissu and Side 2nd are a nice introduction to Kinetic Novels. Kinetic Novels have no choices, you just lean back and enjoy the story that is presented. It is available for free on Steam.
  short (2-10h per part) - Age: all-ages

  The anonymous protagonist is diagnosed with a terminal illness shortly after his twentieth birthday, and is admitted to a hospital in Mito, Ibaraki. There he meets Setsumi, a woman a few years older, who is also terminally ill. Finding that they both reject to die either in hospital or at home, they steal a car and run away together.

• G-Senjou no Maou: Different from the usual highschool-romance-stuff. Unlike other beginner VNs, it has a true route.
  medium length (10-30h) - Age: 18+ // Nudity-free patch available

  You play the role of Azai Kyousuke, the son of a legendary gangster infamous in the underworld. You spend your time listening to Bach, playing God at school and covertly working for your stepfather, a ruthless financial heavyweight. This idyllic existence is broken when two individuals appear in the city - a beautiful girl named Usami Haru with hair you could get lost in for days, and a powerful international gangster known only as "Maou". Almost without delay, the two begin a deadly cat-and-mouse game, bringing you and your friends into the crossfire. Plotting, political intrigue and layer upon layer of interlocking traps are the weapons in this epic battle of wits.

• Planetarian: A good introduction to nakige and KEY works in general. It has an English localization, and you can buy it on Steam.
  short (2-10h) - Age: all-ages

  It is thirty years after the failure of the Space Colonization Program. Humanity is nearly extinct. A perpetual and deadly Rain falls on the Earth. Men known as "Junkers" plunder goods and artifacts from the ruins of civilization. One such Junker sneaks alone into the most dangerous of all ruins -- a "Sarcophagus City". In the center of this dead city, he discovers a pre-War planetarium. And as he enters he is greeted by Hoshino Yumemi, a companion robot. Without a single shred of doubt, she assumes he is the first customer she's had in 30 years. She attempts to show him the stars at once, but the planetarium projector is broken. Unable to make heads or tails of her conversation, he ends up agreeing to try and repair the projector...

Beginner recommendations:

• Steins;Gate: A nice VN about time travel. Has an English localization.
  long (30-50h) - Age: all-ages

  The story of Steins;Gate takes place in Akihabara, and is about a group of friends who have customized their microwave into a device that can send text messages to the past. As they perform different experiments, an organization named SERN who has been doing their own research on time travel tracks them down. The characters must now find a way to avoid being captured by them.

• Grisaia no Kajitsu is a long Visual Novel focusing on characters. There are only 12 choices with a big impact, which is a good introduction to making important choices that affect the story drastically. The Steam version is available for 36€/40USD. Sequels and 18+ versions are being worked on.
  Long (50+h) - Age: 18+ original // all-ages Steam version

  Mihama Academy - on the surface, a closed learning environment established to nurture students who find themselves at odds with the world around them; in actuality, an orchard-cum-prison built to preserve fruit that has fallen too far from its tree.

  Whatever the circumstances behind its establishment, Mihama Academy is at present home to five female students, all with their own reasons for "enrollment." For better or worse, each girl has established a routine obliging of her current situation; life moves at an idle, yet accommodating pace within the walls of Mihama.

  Yet with the arrival of the institute's first male student, the nearly preposterously opaque Kazami Yuuji, the students at Mihama begin to fall out of step with their predetermined rhythms. Will Yuuji prove to be the element the girls around him needed to take hold of their lives once more, or will the weight of their pasts prove too steep a wall to overcome?

  And in the first place, just who is Kazami Yuuji? While the true nature of the "job" he is wont to alight to at the most haphazard of moments remains shrouded in secrecy, one thing is for certain - his encroachment upon the quiet orchard known as Mihama Academy will prove itself momentous in one way or another. And of course, one cannot discount the possibility that perhaps Yuuji himself carries the weightiest past of any of the students...

• Fate/stay night: Another classic. This VN is different from the previous recommendations. It is filled with action, mystery and interesting characters. It has three routes in total, but lots of choices that can lead to one of the 40 possible bad ends. long (50+h) - Age: 18+ original // all-ages Realta Nua version

  ----The one who obtains the Holy Grail will have any wish come true.

  The Holy Grail War. A great ritual that materializes the greatest holy artifact, the Holy Grail. There are two conditions to participate in this ritual. To be a magus, and to be a "Master" chosen by the Holy Grail. (The experience as a magus is not questioned if one has the aptitude)

  There are seven chosen Masters, and seven classes of Servants.

  There is only one Holy Grail. If you wish for a miracle. Prove that you are the strongest with your powers.

• Saya no Uta: If you can handle gore, this is a great VN for you. It is a pretty linear story with three different endings. Written by Gen Urobuchi (Fate/Zero, Psycho-Pass, etc.).
  short (2-10h) - Age: 18+

  Fuminori Sakisaka has a traffic accident which kills his parents and leaves him heavily injured. When he has a brain surgery to save his life, his perception of the world changes: everything he sees becomes blood and guts, people's looks and voices seem like monsters, and food that normally appeals to him tastes disgusting.

  As he contemplates suicide in the hospital, Fuminori meets a beautiful girl among the flesh-covered walls. She introduces herself as Saya, and is apparently looking for her father. Fuminori does not want to be separated from Saya, and asks her to live with him. She agrees.

• Sharin no Kuni, Himawari no Shoujo: A VN where the protagonist is a fully developed character with a unique personality and traits.
  medium length (10-30h) - Age: 18+

  In the near future.

  In a not so distant place.

  There exists a society where law is based upon deterrence and criminals are assigned "obligations" fitting for their crimes.

  Within this society, a man named Morita Kenichi aspires to the position of Special High Class Individual, one who holds authority over said criminals.

  For the purpose of fulfilling his ambition, Kenichi returns to the town he once called home. There he will encounter three girls bearing "obligations" and there he will encounter the past he left behind.

  Won't you join him in this story about how people relate to their society?

  In this story about how a society relates to its people.

  In this story about the girl amid the sunflowers growing in the country spinning like a wheel.

For the more experienced readers:

• Umineko no Naku Koro ni and its sequel Chiru: A very long Mystery VN. Regarded as one of the best VNs with an English translation.
  very long (50+h per VN) - Age: all-ages

  Umineko no Naku Koro ni takes place in the year 1986 during the time frame of October 4 and October 5 on a secluded island named Rokkenjima (六軒島). The head of a wealthy family named Kinzō Ushiromiya, who lives on and owns Rokkenjima, is near death, and eleven of his family members arrive on the island to discuss how Kinzō's assets will be divided once he is dead. Also on the island are five of Kinzō's servants, and his personal physician. After the eleven family members arrive, a typhoon traps them on the island and shortly after people start to get mysteriously murdered.

• Muv-Luv and its sequel Alternative: The first part starts off as a generic highschool galge parody, but the sequel, Alternative, is the highest-rated VN on VNDB, and for a reason.
  long (30-50h per part) - Age: 18+

  • The first part consists of Extra and Unlimited

    Extra: Shirogane Takeru is a typical high school student with a lazy attitude and a love for the virtual reality mecha battle game Valgern-on. Even though he didn't really wanted it, he is popular in school mainly due to his daily fights with his osananajimi (Sumika) attracting too much attention. His life takes an unexpected turn when he finds a girl (Meiya) he doesn't remember ever meeting in his bed one morning. Whom later revealed to be the heiress of one of the biggest zaibatsu. She immediately moves to his house and starts changing his life for the good with her one-track-mind and unlimited resources...

    Unlimited: One day Takeru wakes up late, wondering why Sumika or Meiya didn't wake him up this morning. Not seeing any signs of them he gets a bit worried and goes out of his house to only see the town he lived all his life in ruins. After getting past the initial shock he decides that this must be a dream and decides to enjoy it as much as he can...

  • Because of spoilers, you should choose for yourself whether to read the synopsis of Alternative on VNDB or not.

If you want a specific recommendation, feel free to request it in this subreddit.