Nothing, 'cept for that which is specifically requested, is mandatory for sigs. Borders can be nice to tie a sig together, but sometimes a soft fade on the edges will have a far better effect. It really depends on the rest of the sig, and as with all graphical work you're going to have to make the judgement call of what looks best on a case-by-case basis.
As for glows, I have used just about all imaginable kinds of glows in the time that I've worked with photoshop. Again, it's always going to be something you'll have to make the judgement call on yourself. If you're in doubt then try putting one on, since if you've followed proper procedure and made backup layers (or files) of your work then you can always just turn it off again.
In general, though, if you want to achieve stuff which looks like what I do then try and avoid putting your stuff in boxes. If you look at my work you can see that most of it makes use of transparent areas and irregular shapes, which generally is the biggest diffirence between the stuff I do and that of other sigmakers.
Imagine that you're designing a coat of arms or a medal of honour, rather than a boxed image on display.