Yes, there are. But just a quick word of explanation as to why you're not getting many definitive responses: Keep in mind that the use of compression is very much like working the tone knobs and pickups on a guitar. It wouldn't do someone much good, for example, to ask:
How should I set the knobs on my guitar and amplifier? . Generally speaking, you need to gain an understanding of how they work, and then experiment with them, as every guitar and amp setup is going to be somewhat different, as are the taste of the individual player.
That said, here are a few guidelines for vocal compression settings:
Start with a medium attack ... perhaps a tad on the fast side. Fast release, but more on the slow side of fast. Unless it's a ballad, or if it has slower phrasing (lots of notes being held for more than a beat at a time) -- then you can get away with a much slower release. Usually.
With faster, more up-tempo phrasing, like with rap, you should go with a much, much faster release time. I suppose a good rule of thumb might be: the denser the concentration of words/lyrics in your material ... the faster the release time you can get away with.
Ratio depends almost entirely on how much dynamic range there is in the material (the amount of volume difference between your loudest and softest passages). But generally speaking, the more dynamic the passages, the higher the ratio (or gain reduction) you can/should get away with (try 3:1 or higher). The less dynamic range, then the less ratio / gain reduction is needed (try 2:1 for example). This is also where you have to use your noggin for more than getting kicked in by a bunch of smartass home recorders like us.
In other words, you're going to have to decide for yourself how much compression "you like," and set the ratio accordingly.
As for threshold setting, you'll have to feel that one out. Just set it so that the compression is barely kicking in on your very quietest passages ... but slamming pretty good on the very loudest. And that should usually be a good place to start. Always, always sound check at full volume. Otherwise, the amount of compression and danger of clipping will increase on you dramatically and unexpectedly.
Good luck.
.