I'm taking a trip to Texas (DFW area) and I have always heard about whataburger. What are the things no one should ever miss when trying it out for the first time? I'm looking for:

Main item (preferably a burger).

A side.

A drink (idk if they have some kind of special drink).

A desert or second side if you can't go without it.

At least for my area adding tomato and lettuce is free: So then why would anyone get a premium chicken sandwich when they can get a signature one and add the lettuce and tomato for free. Considering the premium is more expensive then the Signature where i am