Because I've seen a lot of questions pop up regarding tail patterns, especially for canine/vulpine, I thought it might be an idea to share mine...
This is the humble beginnings of this tail: [link]
And this is more or less the starting point of just about every tail I've made so far. Cat tails would be a fair bit thinner, and some like this tail ( [link]
) have had darts added to give it a curve as well as using a slightly more rounded tip, but they have all started from a very similar pattern.
Speaking of darts, those are the little black triangles you can see on the pattern. I photoshopped them in for the purpose of giving an example of how to make a slightly curved tail instead of a straight one. If you were to use a pattern like this one and sew the triangles together (IE: sew the black lines together) and it will make the tail curve. The more darts you add (and the wider they are at the base/edge) will give it a sharper curve. Less darts (and/or a thinner base/edge) will result in a softer curve.