laptop info.....

[snappysi]

Hi all,
i am looking at getting a laptop soon, however must admit that i am not 100% sure on all the system differences. I currently have a desktop that runs everything, internet , email, lightroom, photoshop etc. There isnt anything really wrong with it except it is getting a little slow while editing photos, especially once a few layers are going. The laptop would be primarily as a photo editing tool.
i am wanting a laptop for portability, ( being able to edit anywhere rather than at my desk), running photoshop and lightroom reasonably easily, and be able to shoot tethered in studio.
i dont want to go mac so would prefer windows based.
What i am after is not necesarily a recommendation for a particular laptop, but what i should be looking for as far as graphics cards, processer speeds, how much ram etc......

Thanks in advance..

Simon.