I do go searching for streams. Yes, I have ways of concentrating my search, and am willing to share those. That said, it's quite often that you go to a new stream and find out it's not very good. Even the streams that are good aren't ALWAYS good. A lot of these streams cycle from year to year. Get a couple good years, and the size and numbers are great. Get a rough summer, and the population crashes. And then perhaps for a year or two, as it recovers, the average fish is very small.
As far as finding them, the streams with natural reproduction list is a good place to start. Then off to google maps, toggle between terrain and satellite views of the stream in question.
Mostly forested is a HUGE plus. These streams tend to have less siltation, more stable flows, and run cooler. If there are farm fields and such upstream, I often skip it. The exception may be if the stream is suspected to be a limestoner. Because they often originate from large springs, the warming effect of sunlight may be reduced, as will the siltation issues (less distance to pick up mud).
High gradient is a plus. This mostly limits you to mountainous areas. Valley streams, between mountains, can be good. But even better is a sizable stream coming down a mountain in a gulley. Slow, flatland streams often aren't very good. Again, the exception is a limestoner.
Often if you google the stream name, you can find hiking blogs and such with pictures, which can give you an idea of what the stream is like.
Always gotta keep in mind the chances of posted ground. SGL, state or national forest, and you're in the clear.
Beyond that, being near, or similar in form/source from known good streams is a big plus. A lot of these streams suffer from acid rain. Local rock type plays a big part in the water chemistry and the stream's ability to combat that. Obviously limestone is the best but there are differences between different sandstone, shale, slate, formations. So if you find a good stream, the one next to it that comes down the same mountain from the same general area probably is similar in many respects and worthy of a visit.
Look for impoundments. Usually, below the lake the stream isn't very good. Above it can be good. And if you're really trophy hunting (looking for the occasional big brown or 12 inch brookie), then above reservoirs, or slightly upstream from a larger, richer stream, is good for that.
Other than that, go and see. Always have a backup plan. I've gone to streams that turned out to be posted, or are just so choked with rhodo it's ridiculous, or are horribly polluted with AMD, etc. You go to plan B before even wetting a line! But more often than not, you find some fish and have a nice time. After trying a bunch of these streams, you wind up with a few true gems.