I'm DooMguy and I'll be your tech support for this question
Generally when it comes to laptops, thinner and lighter is better. You really don't want some chunky old thing that overheats after 20 minutes of use. What you want is a cold, slim thing that's also quiet (you really don't want to hear the fan grinding)
It's worth paying attention to the RAM realistically you're going to need at least 4gb to be comfortable. The cpu. . . that's just a long story
As for the HDD, you'll want it to be at least 500gb
Also you'll want a decent keyboard (one which doesn't jam) because. . . well you know, you can't really replace it.
That's just a general overview really. . . but above all of that the true sign of quality is warranty, 2-3 years warranty and it should be good, very good.
Like any computer, it comes down to raw horsepower. Slow and lagging computers/laptops suck and are frustrating to work with. I think Dell makes a decent laptop. You don't need gaming quality, but you want one with lots of ram/memory and a good processor. The amount of ram and the processor speed is what makes up most of the price. You want a laptop that will still be a good performer a few years from now. So you have to buy one that is faster today than what you want. Month after month, programs and software get bigger. Pictures get bigger, websites get more complicated and so on. This why computers seem to get slower as they get older. They actually don't slow down, we just give them more to do as all these programs become bigger and more complicated. So basically buy one with as much memory and the fasted processor you can afford. Unless you are a gamer, don't worry too much about a separate video card. I like laptops with full keyboard with the separate number pad, think most 17 inch laptops are like this.