First - some manufactures have have lists of compatible systems
that they have tested their products on. This will help you ensure
that their product will work on your system.
Second - read about their support. Do they have a data base on
line to help you solve problem? Do they have an 800 number?
Do they have email? You need to know, because when you have a problem with
their product you will need to get a hold of them.
Third - do they have detailed instruction on how to instal their product.