Suggestion 1: Make sure it isn’t a solid blob:) Have its alpha value around 40 or so, that way you can see through it, but still see it. If you have photoshop you could do the “gleam” effect in there, and save it as a .png so you don’t have to worry about alpha values and you can get a nice sparkle effect.
Suggestion 2: Electricity travels fast. If you make it move too slow it might give it a cheesy fake look. But if you make it go too fast, then that isn’t good either.
Since I don’t know exactly how you are doing the motion, these are just suggestions as to ways to make it look real.
Maybe post your .fla or .swf (or both) in a .zip file and attach it to your post, then we can take a look at what exactly you are doing, then we can offer better suggestions. If you don’t want to attach it to your post, can you upload it to a server and put a link here?