I'm starting a big Java project and I wanted to have some advices that could benefit us all.

What are the X (X could be 5 / 10 / ... or even 100 :) most important tips to code and debug efficiently in general (and in particular with java / javascript) ?

I'll start with some basic ones :

Use functions everytime a portion of code is used more than twice. Try not to code features with more than 15 lines of code in one shot. Rather write 5 lines of code then check if they work correctly then write 5 more... and so on start with the outcome of the function and then code it backwards (bottom-top approach) ... Thanks everybody