Steve,

For me the key points are fork geometry, the ability to get the saddle set back far enough from the BB, the reach from saddle to bars, and height of the bars relative to the saddle. I also like a low BB and no toe overlap with the front tire or fender. I would take these contact point specs from your existing bike.

It takes some sketching and figuring to turn those numbers into criteria for a new bike. Setback for example can be translated into seat tube angle, but it depends on saddle rail length and position, and the available seat post setback. But given a saddle and a seat post, you can come up with the seat tube angle that will let you attach the saddle in the middle of the rails - this gives you maximum ability to fine-tune as time goes on.

We can't tune the front end or BB drop, so if you know what you want, you just have to buy the correct geometry. Bar position and height can be tuned. One good reason to start with maybe a 9 cm stem is that you can get a longer one or a shorter one if you need it later. Actual reach to the hoods is affected by handlebar reach and width, as well, so some trigonometry is useful here, too.