I don't think it's too good idea to turn on/off the computer without proper reboot just to force the check. The best would be just to leave the system to do it itself. EXT3 is a jurnalized file system. It means that in case of crash - power outage etc it should restore itself from the jurnal. I remember I read about the message that pops up when Mandrake starts and it asks if you would like to force hard drive check. And by doing this the user in fact disable the jurnal for recovery purpoces. Also the swap file is located on a separate partitition - it means that fragmenting of the files is down to minimum. However if you do want to experiment how FSCK works you may want to learn first how to boot to level 3 (no X - GUI) and then restore to level 5. Read man fsck, man init, man mount, man fstab
good luck!