Should a Buddhist "have faith"? In many religions it is common to say: "Have faith in God" or Jesus or Allah...

In Buddhism we believe in Kamma, meaning that what happens to us is due to our past actions and it is usually not (or never) influenced by an external being. (It can change from school to school, some may pray and ask for things)

So if there is something I want, something I judge important, should I have faith that it will come true? Or should I just do what I think is right and forget about it? What is the best way for a Buddhist to act in this situation?

PS: Please ignore the fact that I want something, I know this could be questioned in Buddhism as the wrong way to happiness, but that would be a different question :)
In the Kalama Sutta, the Buddha is reported as saying that Buddhist principles should not be accepted without evidence, and that 'it is proper ... to doubt'. Confidence/trust (sraddha) in the teachings is important, but 'blind' faith is actively discouraged. Here's what he is reported as saying:


  "It is proper for you, Kalamas, to doubt, to be uncertain; uncertainty has arisen in you about what is doubtful. Come, Kalamas. Do not go upon what has been acquired by repeated hearing; nor upon tradition; nor upon rumor; nor upon what is in a scripture; nor upon surmise; nor upon an axiom; nor upon specious reasoning; nor upon a bias towards a notion that has been pondered over; nor upon another's seeming ability; nor upon the consideration, 'The monk is our teacher.' Kalamas, when you yourselves know: 'These things are bad; these things are blamable; these things are censured by the wise; undertaken and observed, these things lead to harm and ill,' abandon them...
  Kalamas, when you yourselves know: "These things are good; these things are not blamable; these things are praised by the wise; undertaken and observed, these things lead to benefit and happiness," enter on and abide in them.


Kalama Sutta: The Buddha's Charter of Free Inquiry