1. When in a team, be weary on working on someone that's too much connected with someone else's work. Example, if there are two programmers, discuss about the boundaries between your code and your partner's code. Find smart ways to connect your code with your partner's code without getting too deep and having code that requires lots of refactoring.
2. Test external tools/assets on the first day, not the last one. Even better if you can do it before the game jam starts if you already know you'll need it.
3. Don't overthink/think in advance too much. Take small steps.