In most cases, what makes a laptop suitable for gaming is the video card. The processor and RAM are important as well, but you really only need a mid grade one that are sufficiently powerful. Nearly all of the time, the video card is what's going to be bottlenecking your gaming on a laptop so that's what I would look for first. Depending on what company makes the laptop, higher end gaming cards may be uncommon or impossible to find. For instance, with HP, even with customizing the specs on your laptop, you simply won't be able to find a high end card.
Some other things to watch out for are the case and the screen. Gaming usually generates a lot of heat, so a case with good airflow and cooling design are important. If you are going to be gaming only on the laptop without another screen, it's often very nice to have a 1920x1080 screen as well.
When people ask for gaming laptops, I usually assume they want to play games maxed out on 1080p resolution with high fps. If you don't want to do that, then there isn't really any need to get a specialized "gaming laptop". The laptop I use right now is fairly powerful, with an i7 and a mid grade ati 5650. I can run all games that are out right now smoothly on low to mid settings, but I definitely wouldn't consider my laptop anything close to a gaming one. If you really want something that powerful you're going to have to pay 1k+ without a doubt. Otherwise, you should just go with one of the standard i7 + 8gb ram +decent dedicated graphics card laptops that are always floating around for ~$600 - $800, because they'll have no trouble playing any game out there on less than max settings.