READ THIS BEFORE WATCHING THE VIDEO!
What I'm doing is taking two parts of my little sign model, the little bulby part, and the metal ring around it, and unwrapping them.
The bulby part is easy. It's just a hemisphere, with no other connecting parts. It'll unwrap and spread itself out without having to mark any seams. I just select the faces, hit U, and unwrap it. The end result gives me two hemispheres, the front and back bulby parts, which I lay on top of each other, giving them both the same texture space, and align it (fairly badly) over the logo I downloaded.
The ring is a little more complicated. Since it has various dips and bobs in there, doing a straight unwrap might look fairly decent, but it's sloppy, with plenty of faces stretched out of proportion (I really should have used a grid texture to illustrate this, since they're good both for determining texel density, and face stretching). What I did was just add a seam along that bottom most loop, and allowed Blender to unfold it all from there, making a rectangular shape. I did a quick Follow Active Quads command to align it all out, since the unwrapping process does occasionally give you some bendy bits.
From there, I just aligned, and moved the resulting island around. I should've also scaled it up and down a bit, now that I think about it.
In the end, all you're doing when you're UV mapping is just cutting your object into little pieces, in a way so that they flatten out smoothly without any pinching or stretching, then telling that surface where to sit in UV space, which is basically a fancy way of saying "the coordinates where your surfaces sit on a 2D picture plane.
As you can tell, there are some things I wish I did in retrospect, but it's a good primer, I guess.
[MEDIA=youtube]6heDaCp8WJw[/MEDIA]
