The verb PRECISAR is a lot like GOSTAR in that it usually gets followed by a de -- BUT, unlike gostar, not all the time. The de is there because you are literally saying I need of something.
When do you ned to add the "de"? » PRECISAR de
If you're talking about needing a person, place or thing (ie: a noun), always, always, always include a de after the verb precisar.
What if there's a THE after "de"?
If the de is followed by an article, o or a, they contract like this:
de + o = do
de + a = da
*Notice these are all things. Things that you need!
What if you need to-something? Some action - Like needing to buy, needing to think, needing to do something ~?
If you're talking about needing TO DO something, you do not need the de.
Another way of saying this is ~ when the verb PRECISAR is followed by another verb, you don't need the de. (any verb coming after PRECISAR is always going to be in the infinitive)
Needing a thing:
Needing TO DO something:
Não preciso me drogar para ser um gênio;
Não preciso ser um gênio para ser humano;
Mas preciso do seu sorriso para ser feliz.