Instead of trying to "memorize" what is work and what is not, I'd say try to look at the equation and make your own judgements from there. (Sorry if I'm repeating things you already know, btw.) So we all know and love that Work = force * distance* cosine theta. From that definition, work occurs when a force (whatever that force may be, magnetic force, frictional force, contact, etc etc) moves a mass some distance x. What does the cosine have to do with it? The cosine is just another way of saying "only the part of the force that does the moving counts". In other words, imagine you're trying to push a box across the room. If you position your arm parallel to the floor, all the "push" that you put into it will go into moving that box. Now imagine your younger brother who doesn't know anything about pushing or physics, decides to push the box directly downwards. He's using the same amount of force as you are, but that force cannot move the box across the room, can it? So this is a case where no work is done. Yes, there is a force, but x = 0 (in the horizontal direction). How do you know x = 0? Because the box isn't budging. You can also think about it in terms of theta. In this case, theta = 90 ==> cos90 = 0. So W=Fxcos0 = 0, so no work is done.
A very very common example is when a weightlifter holds a barbell directly above his head. Try to use the equation W=fxcostheta to think about whether work is done.
In this case, yes the weightlifter is using a force to hold up the barbell. But the barbell is staying in one place, thus x=0. Therefore, W=0.
Bottom line is, don't make the mistake of memorizing "work = force times distance cosine theta" and plug and chug your way through. An equation is just an extremely shorthand way of writing down the concepts. Try to look at the equation as an "outline", but you have to understand what goes on in between those short bullet points.
G'luck.
BTW, if you're not sick of hearing about TBR by now. I learned all of this (AND MUCH MORE!) from TBR. I didn't do so hot in physics 1 in college mostly because I just looked at an equation as a "rule" to something. And that's the way a lot of people teach it to us: here's an equation, know it, memorize it, and you'll get an A. But in reality, memorizing variables and equal signs is the same thing as studying for an exam from limited bullet points from your friend's crappy outline of his notes.
