What can I do to make the MEPS process as smooth and painless as possible?

Your recruiter should set you up for success. They should provide you with everything you need. A copy of your 680, 2806-2, ssc and ID. Don’t take your cell phone in. If you do, you can store it in a room that they have for you. If you have medical documents for something, provide it all. If you needed a pre read to get to MEPS, it’ll already be there. Just be prepared for them to look into it and the possibility of you may needing to go back to your doctor to get more supporting evidence on it. Get ready for the “hurry up and wait” that you may have heard about. It’s a pretty long process. You’ll just have to tough it out.

Be honest! Even if your recruiter told you to lie. Not that any recruiter would ever do that. Nope. Never.

But seriously, be honest, be yourself, keep calm, and understand that everyone there is doing their job. There is not a single person at MEPS whose job description includes "make sure you take good care of Joe Scafidi".... but no one is out to get you, either. Be respectful and courteous, don't argue, keep a good attitude.

And do what the other folks said, too, about having all your stuff, being on time, etc.

Show up on time with all the things they told you to bring. Do what you're told and be where you are supposed to be. Like most of the military, it ain't rocket science.