Contacts to and from with iMac? Simple? Help?

I think I've read WAY too much into this and am worrying or overthinking it.
iMac, but I never used or added any contacts in address book or the iCal.
New iPhone, contacts transferred over at Verizon. As I've read and read on syncing, I've also come across some threads where people aren't happy with how their contacts appear or are setup on the iPhone. I'm one of them, but can live with it.

So, I have yet to sync with iTunes or plug into my iMac. I do have iTunes setup to NOT auto sync when something is plugged in.

I want/wish to simply sync my contacts from my phone to my mac. Then on the mac rearrange and edit the contacts so they will be more concise (multiple #'s for people, email not assigned to people, etc). I assume this is pretty easy too?

Is there a tab or button in iTunes or elsewhere that let's you choose which way the sync goes? Meaning, from phone to mac or from mac to phone?

My main concern here is; after I sync my phone's contacts to the mac and do the rearranging is then how does it work or what happens when I next plug my phone into the mac to update the contacts/sync? How does it know to delete the phone's old contacts instead or going from mac to phone?
Make sense?
i,e. newly changed on mac's address book...
John Doe had one phone #, his email is listed as jd@blank on phone...now merged or changed under John Doe, so that is now changed on the mac, but the phone still has the separate listings. Next time phone is hooked up, what happens?

FWIW, I have not did anything yet, just trying to understand it before and in-case something drastic happens.

See, told you I am overthinking it.

I appreciate any help or advice!

 

Thanks.

My question still is, does it go by where/on what device the last change was made...if so, then I'm worrying for nothing.

ex: if I add a new contact on the mac, sync, phone is updated? And vice versa?

 

Ok, thought so...just being a worry wart and wanting to make sure I understood.
Appreciate it James!