Quick question... How do you prove you own an address?

[gadman2]

I'm looking for a way to send and receive bitcoins to and from an address to myself. I'm using bitcoin qt but I don't see a want of selecting which address I want to send "from". Only when I click send coins can I actually change which address I want to send to.

[DannyHamilton]

I'm looking for a way to send and receive bitcoins to and from an address to myself. I'm using bitcoin qt but I don't see a want of selecting which address I want to send "from". Only when I click send coins can I actually change which address I want to send to.

Correct.  With the user interface of Bitcoin-Qt you cannot control which bitcoins you send.  The wallet takes care of that for you.  If you want to select specific outputs to be spent as inputs you need a wallet that provides "coin control".

Note, if you send your entire balance from your wallet to a new address in your wallet, then the very next transaction that you send will come "from" that new address.

[Kouye]

And to reply to your title question, the easiest way to prove you own an address is to sign a message using its private key, which is very easy with the QT client (File => Sign a message).