Here's a decent link for help in adjusting the focus of a scope:
http://www.about-shooting.com/Focusing_A_Scope_Reticle
It's important to note that many have a "fast focus" adjustment (i.e. most bushnell, nikon, and others)
And with some you turn the ocular to focus and then a lock ring/washer (leupold, burris, redfield)
They're just a little different and it's important to know that.
Also, this may be of use:
http://www.bushnell.com/getmedia/9a4...e.pdf?ext=.pdf