I found these pages helpful when learning rope work.
Mechanical Advantage Basics
-this page is great. The writer uses rope, prussics, carabiners and some items that you can find around your house. Gives you an idea on how to set us some systems and ideas for practicing.
Knots are the weakest link in the chain. If at all possible, substitute a prussic loop instead of a knot, like at the attachment point of what you are pulling on.
As per non locking carabiners, we had a discussion on the board a few years ago and the general consensus was, if you are going to carry any carabiners on you or your boat, make sure they are of the locking type.