I give players separate grades for their run and pass-blocking skills because the two are completely different animals. In the running game, look for guys that keep their pads and center of gravity low, and have the strength to push the pile backward. Also look for players who have the mobility to get out on the linebackers and engulf them. And keep in mind, the importance you place on run-blocking skills will probably drop somewhat as you look at left tackles as compared to right guards.
A lot of what we covered earlier under Use of Hands and Technique covers pass-blocking skills. At left tackle a team must have a guy with size and athletic ability to match up with the better pass-rushing defensive ends. In general across the rest of the line, keep an eye on how efficiently a lineman gets out of his stance and backs into pass protection. Also watch how well he uses his hands to fight off the defender and control him once they become engaged.
Without going into too much detail, here are some things to keep in mind at each of the positions. At center, obviously you need a guy who can snap the ball. Ideally, you would like a guy who can hold up to the bigger nose tackles in the league, yet posses the mobility to pull or get to the linebackers in the running game. Your guards should have the bulk to clog the middle in pass protection and the strength to push the pile in the run game. The athletic ability to pull and get outside is a nice bonus.
At the right tackle position, a player needs a good balance in his run and pass-blocking skills. He must have the strength to hold up to the bigger every-down ends and the agility to pick up situational pass rushers. The left tackles primary job is to protect the QBs back, so pass-blocking ability is the primary concern. Generally, the most effective left tackles are very athletic for their size and are the best pass protectors on the offensive line.
This lesson concludes the basics of scouting each of the positions on the offensive side of the ball, and now you have all the basic information needed to analyze each player in this unit. After making your analysis, you should be ready to tie together all your information, calculate grades for your subjects, and put together scouting reports should you choose to take it that far.