Say yes to every job, even if there is no money.
Say no when they ask to own all the publishing.
Stall when they ask you to agree to something you think is unfair because often they will cave to your terms from impatience of not getting their way fast.
If the contract says you must indemnify them for any losses incurred because of anything that you do not properly provide make sure to add a new clause stipulating they too must indemnify you if they fail to provide something they said they would but failed to.
If it’s a film and they aren’t paying you much (or anything) at least ask for your credit to be listed 2cnd or 3rd.
If they lie to your face just be cool, smile, finish the job before letting an asshole know that they are an asshole, if you even care to.