Comment One:
To help find an answer to the quesiton of course corrections there is a rule of thumb that I don't use, but I would like to prompt somebody else to describe it properly.
Basically it goes along the lines of (no pun intended): Turn left/right 60 deg and then fly for one minute for every mile you are off track. After that duration turn back on track and get a fix.
That should prompt a respond so somebody please fill the gaps and/or correct it.
Obviously you wouldn't want to do that in anything faster than an Arrow, but for your average PPL I imagine it ends up being a damn sight easier than mental math.
Comment Two:
How about inbound and outbound Fan lines of 10deg. You simply add up the degrees of tack to get your course correction angle. The downside is that you can only correct your course once. The way to get arround this is to make two (or more) shorter legs from one long one and then give each its own set of drift (fan) lines.
Personally I hate drawing lines everywhere so I just stick to doing sums, but each to their own.