The DAO on the hard-forked chain has been converted into a withdrawal contract. You can convert your DAO tokens into ETH using this withdrawal contract - see How do I convert my The DAO tokens into ethers using the withdrawal contract after the hard fork? .
If you bought your The DAO tokens in the last two weeks of the crowdfunding, you will have contributed some ETH into The DAO's extraBalance account. Your original account will be refunded this amount. See How do I get a refund for the amount I paid in excess of 1 ether to 100 The DAO tokens .
Now there are two chains - the hard-forked Ethereum Chain and the non-hard-forked Ethereum Classic, there is a chance of replays occurring. See How to conditionally send ethers to another account post-hard-fork to protect yourself from replay attacks to ensure that your transactions are executed only on the chain you intend the transaction to be executed on.
As you had DAO tokens before the hard-fork, you still have the DAO tokens on the Ethereum Classic chain. The Goodies have retrieved some ethers (ETC) from The DAO contract on the Ethereum Classic chain. See How can I verify that my The DAO token balance is correct when the Goodies provide an ETC refund on the Ethereum Classic chain? as the Goodies intend to refund a proportion of ETCs to DAO token holders on the Ethereum Classic chain.
The easiest tool to use is MyEtherWallet (https://www.myetherwallet.com/). Note that there are some malicious sites using similar names, so make sure you use the link provided here.
On the hard-forked Ethereum chain, you can use MyEtherWallet to convert your DAO tokens into ETH. Then you can send this to your exchange account.
On the non-hard-forked Ethereum Classic chain, just wait for the ETC refund from the Goodies. You should then be able to send this to an exchange to convert it to ETHs if you wish to.