The question came up elsewhere on when to decide if you throw all your SP early in the season or mix and match. For those new to @Ottoneu101 I thought it might be a helpful reminder that there is a 1,500 IP limit, so you'll want to consolidate those 1,500 IP into the best possible IP you can over the course of the season, which essentially means maximizing the P/IP of every pitcher (for those in SABR or FGPTS, "raw" points are only one measure of value, so keep a close eye on P/IP for pitchers). You can monitor the projected IP of your team from the chart at the bottom of your lineup page (see below). Some experienced owners plan to stick as close to 1,500 projected as they can throughout the season, but some will push that projected number up or down as the season goes along while they play matchups. It's much easier to make up IP if you are behind the projection than it is to make up GP (offense) by position, so keep that in mind.
Most importantly though, you will want to throw as many of your 1,500 IP with your five RP slots as possible. The more IP you get from RP the better. 325 IP from your RP is a conservative goal (65 IP x 5), but I would recommend you push hard towards 350+, which means you'll want to both carry 6-8 RP in total, and really watch their usage to "guess" correctly when they should be in your active lineup. You want to own the best RP possible (based on P/IP), but even most replacement level RP's will score more per inning (~7.0) than the very best starting pitchers (on per inning basis).