First take the best value player regardless of any pre-determined strategy. Lean your value slightly toward hitters in order to focus more on them but still if you have a solid SP drop to you where they're a good value you've got to take them regardless of the round.
Second I like to target high K/9 sp's that for whatever reason seem to be undervalued. In one league for example I got Vazquez, Webb, Patterson and Lackey all later on in the draft after taking mostly bats in the top of the draft. Those pitchers won't set the world on fire but they're solid across the board and give a good K/9. I can't stress the K/9 enough in a low max ip league like Yahoo's standard roto (1250 max ip). If you get guys with a low K/9 that eat up innings you'll be hurting in the K category.
Finally you want to look for value closers. If a top shelf closer really slides then by all means take him but in my experience that NEVER happens. What you'll be looking for is young closers without any solid competition or with really good stuff (Valverde, Gonzalez and Fuentes were guys I targeted this year). Fill in all of your RP/P slots in daily leagues...in typical Yahoo leagues with 2 RP and 3 P slots get as many quality MR's late in the draft as you need to have 5 total relief pitchers. Not only do they help with ratios and k's (since they're going to put up very good k/9 and you're limited on ip) but some of them like Scott Shields will actually give you a win/ip ratio as good as your starting pitchers if not better (again, wins don't matter as much as win/ip when you're on a limited number of ip).
That's pretty much what I look at during the draft. No, it's not complicated at all. The main thing is to study up on the average draft position and try to identify some guys that you want to target simply based on their value versus where they're going in most drafts. For example, I knew that Patterson, Webb, Vazquez, Davis and Lackey were all going later than I felt they should be doing. I targeted those 5 guys in one of my drafts and got 4 out of the 5 to fill out my 4 sp's I like to carry. If you have an idea of where people typically go you can grab them right before that and as long as you have enough targets that you can afford missing some of them then you won't have one of those situations where you get flustered during the draft when that one 'must have' guy gets taken.
During the year you just need to stay active, keep on the FA list for closers, trade for value early in the season and to improve your roto position (or detract from your competition's) later in the season. Like 4Pack mentioned, it's not all that complicated. The best thing you can do is to really study the league's standings (especially which categories have the most chance to make improvement) right before the trade deadline...there are some trades you can make to pick up a closer, a speedster or a big bat that can completely turn the entire league's standings on its head. In roto those are the type of moves that win leagues...even if you're losing a bit of value you can win a league simply by getting the right guy to make a difference in the categories you need to move up in.