For a fantasy football draft, an auction is preferrable to a snake draft (and cross country standings/scoring is far preferrable to head-to-head standings/scoring; go read this classic post and join me in the fantasy revolution).
But for a snake draft, I have one key rule:
Draft the player, not the value.
You have to draft the players you want and avoid the players you don't want. You can't get caught up in the "value" of the pick, because the real value of the pick is how it helps your team. If there's a player available you want more than any other player available, and you think he'll be gone by the next round, you must take him; don't convince yourself that it's too early to take him. And if there's a player that you're not really excited about, but you have a feeling he should be drafted or that he deserves a high pick, ignore him: there's no reason to get guys on your fantasy team that you don't want.
You can't worry about "reaching" with a pick. Sure, if you think Player X will be there by the next time you pick, you can risk it. But if you don't think he will be, or think there's a chance he won't be, you have to take him. Don't worry about reaching for the player you want or passing on the player you don't want (or the mockery that ensues): draft the player you want.
This principle cannot be applied entirely to the NFL draft because of the salary cap. If the Vikings really want Robert Meachem, for example, they wouldn't be wise to draft him at #7 because then they have to pay him the money for a #7, which he might not be worth. In the NFL draft, teams do have to consider the "value" of the pick: not the phony value of the draft game, but the financial value that gets associated with earlier picks.
Still, it's a principle GMs should keep in mind. They should draft the players they think are good regardless of where everybody else has them slotted. Or, I believe, they should trade down even if the the trade seems one-sided.
Hypothetically, let's say the Vikings really want Robert Meachem. Instead of drafting him at #7, they could trade down to #15, draft Meachem (the player they wanted anyway), and pay him like a 15th pick rather than like a 7th pick. When you look at it that way, does it even matter what the Vikings would get in return? Even if it looks one-sided, even if people say "Wow, they got screwed--they traded down that far and only got a 4th round pick out of it," the Vikings would know they didn't get screwed. They a) got the player they wanted, b) paid him less, and c) got a 4th round pick thrown in, a pick which they wouldn't have otherwise had. The only negative is that you might have helped somebody else move up without much sacrifice--but you have to be concerned with yourself, not others. Don't worry about perception.
So for the NFL, I modify the "Draft the player, not the value" rule:
Draft the player, not the value; or, trade down for whatever you can get.