Synching Contacts

Apologies if this is a stupid question, but I only have my contacts partially synchronising between my iPhone & mac.

If I add a contact to my Mac, the phone will synch fine.

If I add a new contact to my phone, it will make it to the iCloud but not back to my Mac. This has left my contacts in a bit of a mess.

I realise that one set may need to be a master but is there any way I can get a contact added to my phone back to my Mac contact list?

I'm on 10.6.8 - if I upgrade to Mountain Lion would this start to use iCloud & sort the problem?

Thanks