Thanks a lot guys. Yes, the H bridge is what I was looking into, could you please direct me to some comprehensive tutorial for making an H bridge?
Before you go down that route, you need to ask yourself some questions:
1) What are specifications of my motors (voltage and current needs, particularly worst-case current needs, called "stall current")
2) What is my experience with designing and building an h-bridge (I would say nil at this point, but I could be wrong...)
Depending on the answer to "1", the fact that you have no experience may not be an issue. If, for example, your motors were small "hobbyist" motors pulling only (at max) maybe a few amps when stalled, then not having any experience may not be a real issue, and you could learn a lot along the way. You might blow a few parts, and spend a little money, but what you gain in knowledge and experience will probably outweigh that. If, on the other hand, you are more interested in getting something working, and not looking at how to learn to design h-bridges, then using a motor driver IC (like an L293 or L298) might be the better way to go.
Now - if your experience is low (which I suspect it is), and the motors you need to control have a stall current rating of over, say, 10 amps - you are on "shaky" ground; if they are over 25 amps - I would say forget it. In either case, you might do well to give long and hard thought at what you want to accomplish, and what your end goals are. This is simply because at those current needs, learning how to design an h-bridge to handle them (whether that h-bridge is composed of discrete transistors, or more likely, discrete MOSFETs) is something that could lead you down the road toward spending a lot of money. You could easily end up blowing $5.00/ea USD (or more) MOSFETs on a regular basis. Now - if your goal is to learn - really learn - large-scale MOSFET h-bridge design, then this expense might just be considered part of your education. But, if your goal is to build a running robot, you might end up in a "money-sink" situation.
Just some things to keep in mind and look into, before you make your decision. Good luck, whatever option you take!