1. Tone - Do you like how it sounds? If your horn doesn't sound nice to you, don't get it, even if it's the best looking, "top of the line," etc. You might want to record yourself on different horns to take home to analyze later. 2. Intonation - This is key. Get something like a Korg Tuner and measure each note so it's in tune. 3. Ergonomics - Does the horn feel right to you? Can you reach all the keys? Is there anything that feels weird when you play? If your horn doesn't feel right to you, it may not be a huge crime, but when you're spending all that money for a horn, It better feel right. 4. Brand Name - There are some good stencils out there, but you'll be better off getting a brand name you've heard of. It has better resale value, and it'll be easier to get a tech to fix your horn.

Use the same mouthpiece on all horns that you try - preferably the one that you are most experienced with. If the horns are new, this may not be an issue, but take some teflon tape in case your mouthpiece fits loosely on the tip of the neck. Gaps in there will mess up how it plays - even if it feels tight on the cork at the base of the mouthpiece. This is all assuming you don't have mouthpiece issues. If you are considering switching to a different mouthpiece, you want to do that before you go try the horns unless you are giving yourself LOTS of time to try various combinations. Take with you a selection of the kind of music you play. Play the same selection on each horn. Try out long, quiet notes from top to bottom (as well as loud ones and in between) to get a feel for the response. Is it comfortable in your hands? Switching between horns will always feel slightly awkward. Feeling unfamiliar is ok - you can get used to that you just don;t want to be uncomfortable. Good Luck.