MikeO is pretty spot on when it comes to mock drafts...
I'm probably about as much a junkie for the mock draft glitterati as anyone, and anyone who knows me well will tell you that is a gross understatement. Since the end of the regular season, I have mock drafted either the 49ers or Dolphins "at least" a hundred times (using
http://fanspeak.com/ontheclock/). The vast majority of mock drafts, especially those done by fans of a particular team, can best be subtitled "These are the players I really want" and nothing more. However, there are "real" mock drafts, those done by impartial analysts and so-called experts, that can be looked at as more than just pigskin pipe dreaming. The Kipers, McShays, Mayocks, Brandts and Cherepinskys of the world actually look at pertinent information like the following to make a sincere effort to predict which teams will take which players.:
* What systems each team runs, and how individual prospects fit within each system. Just because a team needs a defensive tackle, it doesn't mean that the best DT on the board is a good fit for that team.
* Contract status of individual players currently on each team's rosters. Teams aren't just drafting to fill their needs for this year, but to fill needs for players likely to leave the next year and the year after that.
* Displayed interest. Which prospects are individual teams talking to at showcase events like the Senior Bowl, Shrine Game and Combine, and which front office personnel are going to which prospects' Pro Days.
Once you factor ALL of that type of information into the equation, you can start to get a feel for which players might actually be selected by which teams. In the end though, it is still a crapshoot, and even the most "sure thing" prediction of a team grabbing a specific player at a specific draft slot isn't ever really a sure thing until their name actually gets called at the podium.