Here are a few little fantasy nuggets I've collected over the years. Fantasy baseball is a game of gaining small advantages whenever you can over the course of a 162-game season. Every little bit helps.
Yahoo's "Trading Block"
Let's say an owner drops someone you want, but you don't have the best waiver pick. Or maybe you're hoping the player slides through waivers. Now's a good time to head over to your trading block and make some changes. Switch up the positions listed, maybe re-evaluate your category "wants." Heck, do it a few times. That player you want is now off the Yahoo "roster move" listing on the main page. Sure, people can check to see earlier transactions, but maybe they won't.
West Coast all the way
Utility players that play in the Pacific Time Zone are substantially more useful then their East Coast brethren. Why? Because you can sit and wait to see if games are postponed/delayed or if a player unexpectedly takes a day off, and still insert replacements into your lineup. East coast swiss-army-knife players are still useful, but substantially less so, as most of the time they've already played when the NL/AL West teams announce their lineups.
Early morning shuffling
It's a pain, but in leagues with daily roster moves, always insert at your UTIL, MI, and CI slots the players with the latest games. It is worth the effort. Trust me. You can stick all kinds of players in these slots, but not if someone already played that morning. How many times have you tried to rejigger your lineup, only to be hamstrung by positions already being locked down? This is particularly important in May and April, when so many games get rained out.
If you're too lazy to do that, at least structure your lineup so the western-most players are in your CI/MI/UTIL slots. Whether he plays at 2B or UTIL, Jeff Kent's stats count the same.
Extra, extra innings
If a team played 15+ innings the night before, bench non-premier starters the next day. Even if they play well, they're likely to be left in too long due to depleted bullpens. Even worse, if they're playing badly, they end up taking one for the team (see: Greg Maddux's game log).
I admit, I'm often too slothful to do this. But why, exactly, do people leave starters in their starting lineup on days they aren't pitching? The only reason they'd come into the game is if it's going really, really long, or if someone gets hurt/scratched. Unless it's a stud pitcher, leave 'em on your bench. Otherwise they may end up taking the field under less than ideal circumstances. This is particularly true for pitchers whom you are spot starting (at home, bad opponents, etc.). You don't want these guys unexpectedly being thrown into a relief role when they've started for years (this happened to A.J. Burnett last month -- it didn't go well).