How is best way to recover the day after a long run? Would it be good to take a slow walk on a treadmill?

that would work, or a slow 20 minute run or sometimes I just get on the bike and spin out 20 miles or so...

Typically I try to aviod doing the same workout for the recovery workout. If I'm reocvering from a long run then its a bike, if a long hard bike then its a short run. Or often times its nothing more than a good stretch. It just depends on how the muscles are feeling.