Actually, I've also just begun competitive battling, so I'll give you a couple tips based on the path I took from advice from the experienced in the art :) . First of all, decide what kind of team I would make. This is going to be how your battling style will be based so choose wisely. There are quite a few sites however that could give you some insight on your decision. Be sure to do some research on the techniques of your team and how to operate it.
Next, decide the tier you will be playing in. There are quite a few tiers in today's current metagame, being U (Uber) OU (OverUsed) UU (UnderUsed RU (RarelyUsed) and NU (NeverUsed). There a few less important tiers as well, but you shouldn't dwell on these too much. Just decide which one of these you will be playing in. Take note, pokecommunity follows OU tiers and under in competitive battls here, so I recommend those tiers. There are also some specific guidelines to follow as well, which you can find on smogon.
Next, begin building your team. This can be one of, if not the most, important factor in your competitive battling. To build your team, you must once again refer back to what team you are going to have. For example, if it's a baton passing team (which happens to be the team I use :D) you would want to include a few sweepers to do the damage. If you are unfamiliar with the vocabulary I'm using, you can learn all that through serebii.net. Be sure to definitely take your time on this one, because you most likely won't get it right the first time.
Finally, get some advice from some of the best. We have some great experts in this department, so I highly recommend asking them about your team in this same sub-forum.
And that's it. I know there may be a few things I may have missed that could be essential to competitive battling, so I would definitely visit the link recommended by that above me :D