So here's the thing, I accidently spilled water on my iphone 4, although it has been fixed, it still get kind of "unstable", sometimes it just suddenly shut itself down.
Since iphone 5 is coming soon, I think I'll wait till then to get a new one.However, I have a pile of important contacts saved on my watered iphone 4 and I'm so afraid that they'll be gone with the damaged phone right before I could get a new one. But if I can copy these contacts to itunes, then next time I'll be able to transfer them to the new iphone,right? Or just copy to computer? Any difference?
Anyway, I just want the contacts to be backuped, any good idea? I use Dell PC with Win 7 system.I don't mind if I have to pay for a tool but it would be the best if there's a free and easy way.Help me please!!

 

1. Open iTunes and plug in your iphone
2. Under the “info” tab you will see a field that “Sync Contacts with :” and give you a choice of which program you want to save your contacts to .By default, it is Windows Address Book.
3. Check the “Sync Contacts With:”box and choose windows Address Book
4. In the lower-right corner click the sync button and all of your contacts will be immediately saved to Windows Address Book
Next time when you want to sync these contacts to your new iphone, you just add them to itunes library, and I belive you know how to do the rest.
Here I find some interesting articles about how to transfer iphone contacts to itunes, maybe it will help you.

 

You may first transfer your iphone 4 contacts to your computer. and that may right there in your “Address Book” on your computer. If “Address Book” is in your dock, the icon is with “@”symbol. If not like that, go to Applications in Finder and do a search for “Address Book”
Next time, do an Address Book export just to have another back-up if you are not automatically backing up using Time Machine, your iDisk, or whatever. If you back up to a file on the same computer, copy it to an external drive.
There're so many trouble transfering from apple products to PC, As a lazy person I personally prefer using a simple software iPhone Transfer Contact, why bother?!

 

You can with the help of Outlook on your computer, create a new folder “Group” under contacts ,then Plug in your iphone 4 to sync with Outlook.
In iTunes select this “group”and make sure to select newly created iphone contacts to save in that same “Group” as well.

I suggest you go to apple's support forum for more information about how to transfer iphone contents from iPhone to PC, once you successfully add the items to to your computer you'll be able to add them to your itunes, there's just one simple step's difference.

A few advice here:
How to transer or backup iPhone contents to PC (iPad/iPhone/iPod to Computer Transfer)
How to transfer contacts from iPhone to Mac( iPhone Contact to Mac Transfer)

 

Yeah if you have Outlook in your computer that might be the easiest way.
Plug in your iphone and there should be an icon show up in iTunes.Click the info tab, and choose to sync your contacts with Outlook. Then, when you get your iPhone 5, do the same procedure. That way, they'll go to the computer, then the new iphone.

Another easy way is to choose "backup" when plugging your iphone to PC, but that will backup everything on your phone.
Here are some similar discussion that you can check on:
How to transfer and backup contacts from iPhone to PC

How to transfer or copy contacts from iPhone to Mac

 

also save them to the cloud, then you can load everything to your new phone after you sync it to your existing account.