Budget is a huge consideration, beyond that, just about any of the big names are a solid choice. Generally speaking Windham ones are pretty good buys.
Norinco ones are usually the cheapest, but they have hit or miss quality. NEA likewise has had some spotty quality control issues.
Beyond that, avoid super short barrels. 7" ones and whatnot have been known to have cycling issues or be very picky about what conditions they operate under. Also, short barrels are louder. Some people like to be that obnoxious guy deafening everyone else nearby, but that's not going to make you many friends.
For the mid-range ones, Daniel Defence are always crowd favourites. They're good stuff.
Keep in mind that any part of the AR can be changed, so if you see one that you really like other than a few parts, you can change it to suit you. Many parts only take a few minutes to swap out. It's not like other rifle platforms where you run into issues of having to completely sell the rifle and start over.