Use the verb mislead to describe what you're doing when you don't tell the whole truth, or when you let someone believe something false.
You mislead someone when you point them in the wrong direction, literally or metaphorically. If you let your cousin think an expensive gift is from you when you actually just sent her a card, you are misleading her. And if you give a tourist directions away from the chain restaurant he's looking for, you are misleading him. Finally, if you think this doesn't really count as lying, you're misleading yourself.