Go here http://www.parktool.com/blog/repair-help and check out the information on headset adjustment. Creaking near the handlebars and strange noises from the front end when hitting bumps could well be a loose headset. If it is a low priced bike there is a chance that the stem/handlebars are flexing and you might have to consider replacing them. The good news is that both are relatively inexpensive if all you are looking for is basic aluminum alloy aftermarket replacements. Stems and handlebars can get expensive, but only if you are concerned about going light weight or special shapes/sizes, neither are likely a concern on an entry level bike.

Here are a couple examples:

http://www.amazon.com/ORBEA-ALLOY-44...rop+handlebars

http://www.amazon.com/Origin8-Classi...rds=quill+stem

Before you buy or order anything, make sure you measure your steerer tube/stem diameter and the clamping surface diameter of your handlebars.