from my experiance, the first couple of months was really, catching up and trying to catch the rythm of what they were doing to me. Getting to know the people. Thankfully, in my bjj, and i think most, there are a lot of humble guys. Cool respectfull guys. I felt very welcomed, and wondered when i was going to be like other who come in and everyone say what's up to... NOW, that happens. I go to bjj and most are like "aaiiiiii clark!!!" so yeah it feels good.
I got a LOT of bruses... Now, i don't know if i'm used to the bruses or what, but i don't get that many bruses. It's like i would bruis easily before. Now minimal.
I was NOT that flexible. To do certain moves, i wouldn't use my hips to get an armbar, or triangle or whatever, now it's better. more flexible more air.
Just remember your there to learn. Just keep learning and don't be afraid to ask.. Usually people want to help, but don't know you want it, if you don't ask. Good luck bro!