Currently Being ModeratedFeb 5, 2013 5:09 AM (in response to DocSilverlake)
If you sign into iCloud on all of those devices, the contacts will sync between them all. Changes on one will be reflected on all the others.
If you are using iTunes to sync them independent of iCloud, I'm not sure how to manage that as I haven't done it in a while.
When I initially set up iCloud, it made duplicates of all my contacts into iCloud, but left them all "On My Mac." All the duplicates I just deleted off "On My Mac." If you have contacts you want on the desktop Mac that you don't want in iCloud, just keep them in "On My Mac" and delete them from iCloud.
If you can't find some contacts, the spotlight index may need rebuilding. You can reindex your whole hard drive by adding it to the Privacy list in Spotlight system preferences, wait a moment, then remove the hard drive from the Privacy list. You should see the little dot in the Spotlight spyglass as it indexes.