I'm not BJJ but I will say that sometimes I go to the dojo with some idea of things I'd like to work on. Other times, I just go with the flow; whatever is being done that night is what I am doing. Every class is different, so it's never boring.
I'm a Kenpo practitioner primarily, however I do also take Ju Jitsu classes as well. I create a flow chart of what position I start in and then if/then situations that result in the targeted submission I am wanting to perfect. It helps me to choose one submission and work to find ways to achieve it from every possible circumstance in different starting positions. After I gain enough competency in the submission that I can achieve success comfortably, I proceed to create a new flow chart for another submission.
Yep. Nice guys. I actually had a white belt ask me this in class the other day. He is brand new and we were getting ready to roll. I don't have a game plan...sometimes. But I do like to find my "bad positions" and find out why they are bad.
When I used to roll....one of my game plans every day was to NOT get submitted. I wanted every match to last until the instructor said to "switch" and go with somebody else. (my plan did not always work)
I didn't have to try and start in bottom position, I seemed to get there every time quite naturally. (rag dolled, lightweight)
But both grappling and stand up (which I prefer) had the exact same primary game plan, which I swear to until this day - when he moves, I move. I may get caught, but it will never be doing nothing, waiting in the position he thinks I'm going to be in.
It wasn't until I got my blue that I started training with a plan. I'll be reading up on 10th planet stuff and intend on using the lockdown while training. I spend a lot of time on the bottom when I roll. I might go "I'm going to work on my open guard" and intentionally create space even though I feel pretty comfortable in closed guard. I'm a big triangle fan so I'm usually in the mindset to create space, setup spider, and shoot for the triangle. In my opinion, the blue is when you should be experimenting with everything to try to find your game. You get your guard passed? So what... that didn't work. Either try it again or try something different. If it doesn't work against a white belt, I can usually just recover. Against a good blue+, I'm probably now in a bad position. That's JJ for you.