As has been said, Blue Chip players are football players or atheletes that put up amazing performances over their highschool careers. They typically come from the more recognizable football states, giving strong incentive to coach for a school in, say, texas or florida or alabama so scouting is faster/easier.
Team Captains affect the morale level of your team. As your team plays, they play progressively better or worse. The more tackles or interceptions a defensive captain gains, the better your defense plays. The more TDs and Yards an offensive captain plays, the better your offense plays. I also believe team captains play a small role in the number of fans drawn to your stadium, and just how loud they are.
As far as I know, you can't court players outside of the post season during your scouting. During scouting though, as no1 mentioned, playing time (especially for the skill positions) is a huge draw to small schools - as long as you have a need at the position. If you try and use playing time to draw a blue chip corner but you have two sophomore and one senior corner on your roster already - and all are playing well - you are more likely to get a negative response than a positive one to the playing time angle.
As a further note, when you're playing as a smaller school and have a glaring need at various positions, decent players (80+ rating normally) will ask for a transfer to your school so they can try to take over a starting job next year. For instance, a Crimson Tide HB in his Sophomore year (Where he's #3 on the depth chart at 81 overall) may try and make a move to UConn where he will be #1 on the chart his Junior year.