PLEASE!!! Wash your gi (and your body) after EVERY time you train! Don't go out to eat or shopping first either. The longer the bacteria sits on your body, the more likely you are to be contaminated or spread it to others.
Also....if you see anything suspicious on your skin DO NOT come and roll with the rest of us (even with a bandage on it) until you are sure it is no longer contagious. This can cause a HUGE out break through out the gym. If you are not sure what it is, please ask one of your instructors. Chances are, unfortunately .....that they have seen it or had it in the past and can let you know if it is something to worry about.
Staph Infection (This is no Joke!)
If your gi is stinky: Use Vinegar, it not only will help get the smell out, it also helps to preserve the colors in black or blue gi's (or any other color) it kills odors without weakening the fabric. It also kills germs and is all natural.
Washing your gi: you need to wash your gi every single time you roll. Don’t overload your washer! You gi will not get clean. I like to use Tide Sport (it smells good and helps remove stains) you can also use Baking Soda or Borax.
Line dry your gi: The Sun kills bacteria naturally. Dry your gis completely before wearing them!
A common cause of funk is to wash the gi then wear it before it’s completely dry. Moisture is an environment that bacteria enjoy, and if you never allow your gi's to dry completely, you’re probably harboring plenty of funky bacteria.
I personally don't put my dirty gi back in my gym bag (unless you want to wash that too) It also can hold bacteria.
Keep fingernails & toenails trimmed as-well.