Being a long-time skywatcher, I've learned what to look for, where sunset potential is concerned. The main consideration is cloud cover. That's not to say that you can't have a beautiful sunset without clouds, but clouds really pack that added punch. They act as a canvas for all of those long-wavelength light beams to paint their brilliant colors upon. Different cloud formations produce different effects (including the lovely & rare sun dogs.) Clouds on the sunset (west) side of the sky can also offer interesting breaks for the light to travel through, creating the potential for lovely crepuscular effects. Clouds don't have to be on the sunset (west) side of the sky, however. So long as the long-wavelength light rays can reach them, they'll color up any & all clouds in the sky (note that the effect generally travels east to west as the sun goes down.) The only one place you want to avoid all cloud cover is along the western horizon, which would block the light from getting through, to begin with.
The next consideration is framing or setting. When I see the potential for a really nice sunset, I look at 2 factors; where I'm going to take the photos & how long I have to get there. If you don't know what time sunset is, hold your hand out at arm's length, fingers parallel to the horizon. Each finger width between the sun & the horizon line roughly represents 15 minutes.
As far as setting goes, if you're in the middle of the woods (like my house is,) the trees are largely going to get in the way. Not that that's a BAD thing, mind you, but to me, sunset photography is all about the sky, so I head for open areas. There's nowhere more open than a body of water, which offers the added benefit of the water reflecting all of the beautiful things going on in the sky. Sometimes the sunset makes a nice backdrop against other elements, however. As with anything artistic, beauty is in the eye of the beholder.