Well, I have a JKD background and just singed up for BJJ with Helio “Soneca” Moreira since he moved to Knoxville. They train hard, offering classes 2x per day including plenty of no gi work. As a beginner in this style, I wanted to ask you advanced dudes if you have any basic advice as I begin this path?
Welcome and empty your cup of tea, bring a notepad, brain storm the right questions, practice practice practice, and be sure you watch your diet and fluid intake. Oh and find a way to hit the water (pool or beach). I am not advanced, but I know how to learn and recover.
Relax, open your mind and don’t worry about beating anyone or impressing the girls watching.
Drill the fundamentals and leave the flashy flying omoplatas to those in the Mundials.
find a purple belt. tell him you have a black belt in karate or kung fu, or whatever. tell him that means you are better than him and you can kick his ass. then have fun with it. 
seriously, just be ready to have a lot of fun. i’ve been doing bjj for about 8-9 months. so i’m far from an expert, obviously, but i have a blast. i’ve seen two types come through the door in my short time. the first type does it for a couple of weeks, maybe longer, and then disappears. the other type starts out once a week, then moves it up to twice a week, and pretty soon is going as often as possible. it’s quite addicting. you get over the gay looking aspects of it pretty quick.