Dovetail angles are often described by the ratio of rise to run. Historically, in the western tradition, dovetails would be made with an angle of 1:6 for softwood, and 1:8 for hardwood. This equates to about 9.5 degrees and 7.1 degrees from normal to the end of the board, or basically 9.5 or 7.1 degrees away from being a finger joint instead of a dovetail. Some people feel that the easiest way to get by in the dovetailing world is to use 1:7 on all material as a compromise. This equates to an angle of about 8.1 degrees.
My question, of course, is who cares? We're talking about less than two and a half degrees difference between the whole range of them. Who is going to be able to tell what ratio you used when looked at from any kind of a distance. A person with a good eye might be able to guess, but you'd need to take a gauge to the piece to be sure, and anyone who takes a gauge to anything I made deserves whatever disappointment might be forthcoming. :)
So what do I use? I use the 1:6 ratio for all woods. I figure if it's going to be a dovetail then I might as well pick the one that looks the most like a dovetail.
Below we see a quickly cobbled dovetail that I just did this morning for the sake of illustrating this point. This joint has two tails. One is at 1:6 and one is at 1:8. Even right side by side and zoomed in it's not that obvious that they're different angles. At most you might think that it was a minor variation caused by hand-cut joinery. Certainly it wouldn't scream at you from across the room. So I, for one, don't get all excited about dovetail angles.
Frank Klaus, master cabinetmaker and father of dovetail excitement on this continent, doesn't use a gauge. He eyeballs the angles. He doesn't even measure out the spacing. He eyeballs everything except the depth of the cut (which must match the thickness of the board being joined to). Despite his carefree methodology, his experience is legendary and he can cut seemingly air-tight dovetails in the time it takes most experts to do the layout.