What do you use as a "break point" to determine your next tier? Is there a mathematical number? Or do you just use a "gut" feeling?
I use a 5% dropExample using current WRs
Steve Smith projected as #1 WR at 192 pts, a 5% drop would be approx 182 pts, so anybody projected at 182+ is in the same tier with Smith (that's Holt, CJ, Fitz & Moss).
The next tier starts with Boldin projected at 177pts. 5% drop would be 168pts. Anybody projected at 168+ is in this tier.
Next guy after that tier is Roy Williams at 163, 5% drop means anybody at 155+ is in the same tier.
I don't claim that this 5% was arrived at by any super-secret method but I figure 5% is an acceptable margin of error and probably better then you'll actually find in most projections. My thinking is that if my projections can be off by 5% in either direction then, logically, any WR with projected points 5% above or below the guy I'm looking at is "just as good as" this guy.
One thing I like about running a "hard number" is that it will bring some stand-out guys NOT in the top 10 or 15 to your attention. You'll find very small tiers (perhaps only 1 or 2 guys) that you'd be tempted to lump in with the tier above or below if you strictly did it by your gut but by running the numbers they'll jump off the page at you. If you can isolate 1 or 2 guys that are clearly (at least 5%) better then the tier below them you can really maximize your picks in the middle and late rounds.
One last thing; after I tier my players I erase (or at least don't print) their projected stats/points AND shuffle the names up within the tier. If you're gonna trust your tiers, you gotta trust them all the way. If all the WRs in your 5th tier are truly "equal" then treat them equally. By shuffling them up and erasing the crutch # I find I'm more apt to sift through a tier for the guy that best fits my roster as it's being assembled rather then on the fact that one guy was projected with 878 yards and the other with 868. Watching bye weeks, or avoiding the WR2 on a team that you already have the WR1 on, etc, etc. I've found that I assemble more balanced and better constructed teams this way.