Martial arts general thread?

Going to be starting Brazilian jiujitsu next week with my old karate instructor of around 4 years or so. I've dabbled very lightly in BJJ before but I want to know what to expect seriously training 3-4 times a week. Tips on getting cardio up fast? Should I look into elbow and knee sleeves to avoid mat burn? Are Lycra shorts preferred amongst fighters for no-gi training?

I don't know how the gym operates but of my sensei attends it its highly likely to train very strictly on form, technique and terminology, which is how I prefer to get it done.

Tips? Also share your experiences and training styles. Cool stories are welcome.