If you have both eth and etc. As the eth was created in the genesis block and etc has the same genesis block. You can open the json file in note pad and it will show which eth address it is sitting on if you want. That address will be the same on both chains right now.

You can then check how much etc you have here:
http://gastracker.io/addr/0xyouretcaddress

Now as for moving one without the other that is a little bit more tricky. You can use the splitter contract at address 0xaa1a6e3e6ef20068f7f8d8c835d2d22fd5116444 to split them(Vitalik talks about it here https://blog.ethereum.org/2016/07/26/onward_from_the_hard_fork/).

But if you are trying to keep the genesis eth wallet untouched that won't work. What you can do is transfer one etc into the address that you know won't be on the regular eth blockchain and then transfer the whole amount of etc over to a different address.

You can do the same with eth just move a after fork eth over and then move all the eth.