A super novae appear somewhat regularly, but one can never tell when & where they will appear. I say somewhat regularly only because of the sheer number of galaxies that there are. But, the occurance of super novae in any one galaxy, including our own Milky Way, is very irregular, and with a very long time between each.
When one does get discovered in another galaxy, all you will see is a single star that will slowly rise in brilliance to a maximum, and then slowly peeter out. The whole thing happens over a month or two.
A super nova can exceed the brilliance of its parent galaxy by a few times - that means that an exploding star can be 2, 3, even 4 times more brilliant than the 1 trillion stars of a galaxy.
Unless the super nova happens here in the Milky Way, like I said all you will see is a pin point star. The way to identify it is by comparing your visual or photographic experience to other photos of the same galaxy where the super nova wasn't there.
At the moment there are no super novae visible. If you would like to know when one does appear, they are mostly posted in the
Astronomy & Amatuer Science forum.
Australian amateurs have quite a track record for discovering super novae. In fact amatuers discover more super novae than professional astronomers by the single fact that there are just so many more amatuer scopes pointed at the sky than professional scopes. This is just one aspect of astronomy where amatuers are making a REAL contribution to science.
PS, I stand corrected with there being no super nova being visible at the moment (thanks Lee!). Have a shot at the one in M65. Thee should be some info on this super nova somewhere in IIS or another forum.