When Eddie was a pup he would pee in the condo all the time - the most aggravating part was he didn't do any pre-pee ritual like sniff around, a little whine, walk in a circle, nothing - nothing to give me a heads up what was coming.
So I needed to teach him to let me know when he had to pee - my solution was a medium sized christmas bell on a string tied to the front door handle.
Every time I took Eddie out I rang the bell as we were leaving - in three days he was batting at the bell to go out - success.
There was one small speed bump - Eddie knew that ringing the bell meant going outside - so I had to determine if a bell ring meant he had to pee or he just wanted to go outside. After calling his bluff a couple times - he only rang it when he had to go.
Eddie is almost 2 now and the bell is still on the door and he still uses it every once in a while when standing by the door doesn't get my attention.