Don't just post a request for help in a forum and expect someone else to solve the problem in your code for you. Unless the problem is trivial and easily corrected (eg a semi-colon in the wrong place) then the chances of someone handing you a complete answer is not all that great. Of course for the expert many of the problems they can't solve will be of the trivial/easily fixed variety since these are the ones that are the hardest to spot since you are most likely looking for something far more involved and overlook the most obvious. Something someone else will spot for you straight away of course which can make you look stupid but it's really a case of being too close to the trees to see the forest.
Before posting a request for help you will obviously have done some testing (otherwise how do you know it doesn't work). If you make a note of what tests you have already performed in your request for help then you will reduce the amount of testing that others will need to do to help you out as they wont need to repeat your tests. This will also improve your chances of someone actually helping you as they can see that you are not expecting to be handed the answer without working on it yourself.
Often you will also get responses that are not the solution to your problem but rather are suggestions of things for you to try that may help you to work out what the problem is. When you do get such suggestions make sure that you try exactly what is suggested and see if that resolves the problem. Of course even if it doesn't it will at least provide further information for you and anyone else who decides to help to further narrow down what the problem might be. It may even suggest to you other tests that you can perform that might progress things even further. Make sure that you add the results of these tests to the forum where you have asked for help to save others from wasting time suggesting things you have already tried.
Finally, when you do work out what the problem was, add that information to the forum as well both to let the would be helpers know that the problem is solved (and that you therefore no longer need their help) as well as to let anyone else who has the same problem in the future know how to fix it.