We sometimes think that du'a is just to raise hands and say "O Allah, give us this and that". As a matter of fact we may not get what we expect in the prayer. However there are various sorts of duas.
One of the most effective ones is "active dua" or "dua through action" (du'a fi'ili)that servant does as much as he can to make his wish true. After "active du'a", he makes "oral du'a"...
If we fall short of fulfilling the requirements and do not do as much as we can, our prayers are incomplete, too. If one does not do whatever he ought to do and plainly ask for success, at the end of the day he would possibly be failing, thus has no right to complain as if he had done everything he could have done, and no right to say that "Well, du'a did not work".
We should be mindful of the fact that He is Allah who has given the tongue and hands.
Allah is the one and only Creator who creates our wishes. There is no-one except for Him that can create something and put forward into the realm of existence. Abilities granted us by Allah (SWT) are all duas and He is Allah who creates the results.
Solution:
Step #1: Do as much as you can (active dua)
Step #2: Make du'a (oral and qalbî du'a)
Step #3: Tawakkaltu 'al-Allah
