The CPU of a gaming laptop should be powerful enough. So feel free to choose only the model with Intel Core i7. With a very limited budget - Core i5. From AMD for gaming laptops suitable hybrid processors of the sixth generation. This is a model with indices FX, A10 and A8. For any choice of the processor the amount of memory should not be less than 8 GB. The more the merrier.
From the point of view of the video card, the choice is much richer. If the budget allows, the price of this laptop is around $ 3,000, it is better to buy a dual graphics card. This technology is called SLI for Nvidia, and AMD - CrossFire.
If you are targeting a more modest budget, about $ 2000, then stop your choice on Nvidia Geforce GTX 980M or 970M. This is quite a powerful graphics card, capable of providing high performance in games.
With a limited budget it is better to buy a normal laptop with Geforce 840M or a AMD R7-M260DX, but not necessarily discrete. Integrated graphics solutions are unable to provide the required performance in the games.
It is better to choose models with a mechanical keyboard. These are specially made for professional players. Membrane keypad, installed on most standard office laptops can quickly fail and not so well in 3D shooters.