Don't buy a laptop if not absolutely necessary. If you do absolutely do need to buy a laptop then I would suggest searching for one with a non-mobile graphics card. Here are some examples and reasons why:
If you have a 144hz monitor you have to get a DVI-D (Dual link) cable port on the laptop.
Be aware of a number of USB ports it has.
Buy a laptop with a 1080p display.
Be aware that a laptop is noisier than a desktop PC because it has less space to hold the heat, therefore, the fans spin quicker so you might want to acquire a headset (I use HyperX Stinger from Klingston* which works really well).
Feel free to question or correct me if I said anything wrong c: