Trying to manage music. Help!

Finally decided to buckle down and create some playlists in iTunes. At first, I tried just going through my library and dragging songs to the corresponding genre, for instance. But I realized I was putting some of the same songs in different playlists. So then I tried unchecking all my tracks and just checking the ones I wanted going into a specific playlist. Very tedious, but I guess that's what I get for waiting so long. ANYWAY, I was just wondering if there is a way to mass select the "checked" tracks instead of selecting them one by and dragging them to the playlist. Also, any other tips or ideas would very much be appreciated. Thanks!