I found some videos that prepared me for cutting my husband's hair and eventually I will cut my sons hair too. I like their hair a little longer and not buzzed. Below are the ones that I found most helpful.
My Step by Step Haircut For A Child, Boy, or Man (Part 1) Easy Hair Style Cutting Tutorial (Extremely helpful!):
And Part 2:
Of course when I did my husband's I used the first guard (the one that keeps the hair the longest) and used the clippers on it till towards the top and then I used scissors on the top.
I have yet to do my boys but my husband's turned out really good. I guess I will get to keep practicing. I mean its just hair it does usually grow back right?