1) Stick to WR Percy Harvin
Charles Tillman was deserving of his Pro Bowl nod, but he's had games where he's shut down the other team's best receiving option (Calvin Johnson Round 2) and other games where he has been lit up like an atomic Christmas tree (Vincent Jackson, the very next week). As the team's best wideout, Harvin will be lining up against Tillman, and with Adrian Peterson out with his knee injury, Harvin becomes the team's strongest weapon (with all apologies to Toby Gerhart). Tillman will have to stick to Harvin when he's out wide, and for those instances he lines up in the backfield, he'll be targeted by the speedy Bears' linebackers.
2) Know Which Quarterback is Playing
This may seem like a cop-out. The problem is that Ponder is probable with a concussion, but has been pulled in two of the last three games in favor of the quarterceiver Joe Webb. So the Vikings have a question - play an occasionally-struggling first round rookie who just suffered a concussion, or play with an interesting gimmick quarterback that has skills and excels with the ball in his hands. If it's Ponder, the Vikings will have a little more balance to their offense, but if they sit Ponder in favor of Webb, look for the linebackers to generally stick to run-stopping and leave Tillman and Tim Jennings on islands against the Vikings' receivers.
3) Defensive Line Wakes Up
Whatever the defensive line has been doing the last few weeks, can they stop that? The lack of pressure all across the board has been just brutal to watch. The line needs to show up and hit the quarterback/running back early and often. Both quarterbacks are solid threats to scramble/run the ball, so the line can't let the offensive linemen dominate them like has been happening the last few games.