How do I sync my contacts on my new iPhone with a Mac?

I just got a new iPhone and I am having trouble with my contacts.

I had a Droid phone previously and all of my contacts synced w my Gmail account.

Now I have a new iPhone4 and I want to sync my address book with a Mac.

I got my Dad's Mac from him b/c he does not use it anymore.

I am trying to get my contacts synced to something (iCloud? Mac contact book?) but i am afraid that all of his contacts will end up my phone.

Any thouhgts?