Keep in mind that Lycoming and Continental have different fuel systems, and slightly different hot start procedures.  This procedure has worked consistently for Lycoming 320 and 360.
The problem is that the fuel in the lines vaporizes, as has been said earlier.  Also, you will need to adjust your priming depending on outside temp and whether the plane has been shut down for 5 minutes or 30.  But the procedure is the same, and in my experience, the best.

HOT START
==========
Throttle set 1/4 (ie 1200 rpm)
Prop IN
Mixture Cutoff
Fuel pump ON
Mixture Full Rich, 2 seconds max (adjust as necessary)
Mixture Cutoff
Fuel pump OFF
Throttle Full IN
Wait a couple seconds, crank engine
Upon firing, slowly advance Mixture
Throttle back 1000 rpm

If that sounds similar to Flooded Start, it's because that is the best way to clear the vapor from the lines.  There are variations, but hope that helps someone.

 D. Story