of the many brands and prices, how do I pick the best balsamic to start experimenting with? My principal use will be in salads.
Is there a shop near you that does tastings? I spent a fun afternoon recently trying different vinegars in a local specialty store.
Cook's Illustrated often tests products and publishes the results. The magazine--or website if you have a digital subscription--is always a good place to start.
Fini is a good brand (for commercial as opposed to artisinal balsamics). From Modena in Italy.
You might also do a comparison with good quality, aged Spanish sherry vinaigrette. Often a better value with better flavor.
Aim for a balsamic that doesn't have added sugar or artificial additives. Good ones will have an age on the bottle. 5 years or less will be fresher and sharper whereas 25 years or older are likely to require you to take out a second mortgage and probably only for the expert or the wealthy!
I get my good stuff from http://fioreoliveoils.com/site/ . I have been to the store and did the tasting... have yet to find anything better.
I've used Alessi in the past for marinades and it has worked fine; not too costly either