The key is actually freshness, as with all good foods. I believe you have a better chance of getting good fresh ingredients if you buy your tea loose, rather than bagged.

As a one cup at a time drinker, I am a great fan of tea infusers, which keep most of the leaves out of my teeth.

For those of you who are in it strictly for the taste but not the caffeine, you can dip the infuser for about 10 seconds in hot water and then move it directly to your brewing vessel, be it cup or pot.