QUOTE(eldatom @ Dec 29 2008, 02:02 AM)

Took mine when I went to try out the pianos, I figured how would I know if it was the right piano without playing the pieces that I was working on. I made sure that I tried fast slow, legato and staccato so I could see how everything felt.
The man in the shop didn't mind at all and he kept out of my way unless I asked for his help.
ET

Totally agreed... I did the same. I brought my Sonatina album and my exam pieces. And I played so many times that people started to stand around listening, or rather, waiting. But can't be helped, I had to test!
Definitely choose a piece that you are good at playing, so that you won't suffer from stage-fright, or stumble over notes. I think a Sonatina is a good idea, because:
- there are usually 2 fast movements and 1 slow one, so you can test some staccato, fast running passages, and some legato, even some pedalling
- there are ornaments, so you can test how responsive the keys are
- there are ff and pp dynamics, so you can figure out how loud and bright, and how clear the piano sounds
If you have exam pieces, you could test:
- how suitable the piano is for bright jazzy pieces
- how suitable the piano is for milder classical pieces
- whether the bass is clear or muffled when you play some counterpoint music
- ornaments
With pieces, you can easy identify a piano that is off-tune. If you notice one that is obviously out of tune, ask the salesman. You can also test the integrity of the dealer. Some salesmen refuse to admit that there are problems with the test sets. "Buzzing sound? No, that is just the lamp over there!"
Also look for some passages to test the pedals, both left and right.