Read the following thread. This is a great place to start.
http://www.subsim.com/radioroom/show...01&postcount=1
When you want to begin using manual targeting, read Hitman's tutorial on Manual Targeting at 100 Percent Realism. Also, go the Skipper's Bag of Tricks sticky thread in this forum to learn about O'Kane, Cromwell, etc.
And then, there is the Easy Aob mod, but that will take some explaining.
Do you have Skype?