Like Fenhorn says.
Also, breaking someone by doubt is a very aggressive move. You don't do it unless you really want to break someone. If you don't want your opponent broken - don't break him.

Offer something in return instead.
Also note that breaking someone by doubt on a single roll is really hard - remember, only additional sixes (beyond the first one) will cause doubt. Thus, breaking someone with an average Empathy score of 3 will require four sixes in a single roll.
Oh, and regarding your other question - your return favor (when
not breaking the opponent) doesn't necessarily need to be given before the action that you want your opponent to perform. Your opponent might just as well ask you to promise to do it later - it's all up to you whether to accept the deal or refuse it.