First thing you need to know is what kind of display you want.
Do you want 15,6 or 17,3 inches.
Most of the people go for 15,6 but if you don't need to carry it around a lot 17,3 is a great choice.
You want Intel because at this time AMD just can't compete with them. Go with i3 or stronger (i5,i7)
At this point 4 GB RAM is a must . Anything above is better.
It would be ideal if laptop has dedicated video card like Radeon or Geforce. Internal graphic cards still can't compete with dedicated ones and you will have much better performance in games and video because of dedicated graphic card.
At this point Windows 10 is pretty good but if you are used to Windows 7 you can install it too. It's still really good OS.
This really doesn't matter that much. Every brand has its good and bad sides. If you want something you like with good specifications for a good price pick that no matter if somebody is saying things like "don't go with Lenovo" or "HP always break fast".
Good luck with buying your new PC.