One thing that helps determine what you should be drafting is the number of teams in your league. Take a look at where certain position tiers start to drop off based on your point system. Then you can kind of calculate what round it would be appropriate to draft a particular player. There is a huge difference between 8 team leagues and 14 team leagues, especially at WR.
As GTripp said, once you get passed (past?) the top 3 or 4 RBs, then the elite WRs and QBs are fair game because the rest of the RB pool is pretty even. If Frank Gore were not injury prone I might would put him in the elite category btw.
Check out the
fantasy football calculator website. You can jump in a mock draft that fits the number of teams in your league. It's nice because it gives you a feel for who's going where and in what round. Forinstance, I've got the number one overall pick in my 14 team league. The first pick isn't a big concern for me because obviously I'll get an elite RB, but my 2nd and 3rd pick falls at the #28/#29 spot. At that point, your top tier QBs and WRs are gone. Now I need to decide what spot I'm going for. Certain positions really start to thin out like RB and WR, whereas QB and TE are pretty thick. So, I usually pick two wrs then a QB/TE, maybe a RB. The strategy isn't set in stone. I mean, I'll Forte or Grant as my 2nd RB if they fall to me in rounds 2/3.
That's my two cents.