Best Way Or Tool To Check Headspace?

[MOOSE 4 GOD]

[I][COLOR=darkblue]How important is headspace and how do you make sure you do not have excessive headspace? What is the best way or tool to do this with? Foster makes 3 types a go guage/ no go guage/ and a field guage. What is the differance? LE Wilson and Stoney Point makes what is called Cartridge Head Space Guage for a lot less. I'm confused Anyone who can clear this up in laymans terms for me I will truly owe you one.

Thanks so much for your time
Benny Moses