Help with bike!?

I just got a new bike from a friend. I noticed that when I hold the of handlebars straight, the wheel actually curves to the left instead of sitting straight. It's like the alignment isn't right. Does anyone know how to fix this problem. When I ride the bike, I feel like I am having a difficult time controlling it, cause the handlebars are weird. Thanks!

loosen the bolt and the top of the goosneck (that thing that hold the handlebars on) hold the tire between your legs, straighten the bars to the tire and tighten the bolt back up.

If the handle bars are connected to a stem, then I can help you.
The Handle bars are held on by the stem, and that is connected to the fork. There should be one bolt on the top, you want to loosen that a little, then there should be two bolts on the stem that you will want to loosen. Realign that, then tighten the two bolts down, then tighten the top bolt. Here is where you want to be careful. If you tighten it too much, then it will grind when you turn the handle bars, but if you leave it too loose, it will shake too much. The way to check for this is tighten it somewhat, then pick the front tire off the ground and feel how it feels turning right to left, if it feels ok, then put it back down, hold the front break (but not the back) and try to rock the bike front to back, if you can feel play in the headset, then it is too loose. Good Luck!

If it's a threaded gooseneck (one-piece with a bolt at the top) remember that you have to loosen the bolt a good half an inch then whack it with a wooden mallet to break the hold of the split-wedge in the headset. It won't adjust unless the wedge is loose.

It depends on the type of bike you have. The easiest and most accurate way I have found to "true" handlebars is as follows.

A) Remove the front tire of the bike. This should be easy, as most bikes nowadays have quick release skewers, as opposed to the old axle bolts.

B) Loosen the allen screw located on top of the headset. This can be found directly behind the middle mounting point of the handlebars, and will be a recessed 6-sided hole. You will need an allen wrench to loosen this nut. Don't worry about taking it all the way out; a 1/2 a turn or so should be loose enough to twist the mounts.

C) Stand the bike on end with the back tire up in the air so that both ends of the handlebars and both ends of the forks are the only things touching the floor. This should work even with gear shifters and brake levers, as that all should be rotated towards the rider. Make sure you do this on a towel or newspaper to avoid scratching the bike, or hardwood floors.

D) Re-tighten the allen screw. If you are working alone, you can lean the tail of the bike against a wall or counter. If you have someone close by, simply get them to hold the tail while you tighten the screw.

E) Re-install the front tire. You are now done, and the handlebars will be trued to the forks, unless something is bent.

For further reading, I have posted a website in "sources" that details the proper way to loosen and tighten both threaded and threadless headsets. The only difference is that your bike will be standing on end as opposed to wedged between your legs.

Good luck, happy riding.