Some of those things you mentioned are important, but the way to go about it is to find out whcih CPU are compatible with your motherboard so you can:
A) Contact the Laptop manufacturer and ask which CPUS are compatible.
B) look at teh same model laptop sold by the manufactur, but the higher end model and see what CPUS they have.
C) find out what the model and manufacturer of the motehrboard is and contact them.
D) Do some googling and find out what CPUs other people have upgraded the CPU in the same model laptop to.