Think in terms of the mean
In junior high, I remember learning that the mean was simply the mathematical average. In the world of fantasy baseball, the mean is the concept that should allow you to sleep easy at night when David Ortiz is on your team and hitting well under .100. If Ortiz hits .300 for the season, you should be getting a .330 hitter from May through September.
Unless a player is going into serious decline or is in the infancy of a career, you can generally assume that most players will catch up to their career norms after a slow start. By the same token, a player that is absoulutely on fire for the first month will see a market correction over the course of a season.
Panic is often the emotion that many fantasy players demonstrate when their players are crawling out of the gate. Here is what I suggest for fantasy owners:
1) If your players are slumping, try to get a bench player to step in for the short term, then as soon as your player starts to heat up, get him right back in the lineup and let the good times roll!
2) If your opponents have slumping players, try to make a reasonable trade offer that might make them consider making such a deal. I urge you not to make a ridiculous offer so you do not raise emotions amongst owners that will make them ignore any future offers you might make.
3) Keep reminding yourself that every slump turns into a hot streak, so stay the course!
On some of my teams I have David Ortiz, Miguel Cabrera, and Erik Bedard. I am not worried about any of them and I know that they will be team leaders as the season moves on.