Now, you don't want to start lying about how Eyonix is your GL (#7), or stand outside Karazhan trying to show off (#4), but there's nothing wrong with making sure people know that you're progressing. Have your guildleader post on the forums when you make a big kill, or throw out a few yells when you're about to give out a zone-wide buff (I remember when my guild turned in the Onyxia head way back when, and we did a nice parade through the center of Orgrimmar, all decked out on our mounts). A great video helps, too-- a funny recruitment video will get you attention, but a how-to video for a tough boss your guild has on farm will attract exactly the kind of people you want on your team.
You should never try to steal raiders from other guilds-- guildleaders have a hard enough time keeping a raiding team together as it is without teams fighting amongst themselves for players. But there are always good ways to "advertise" your guild to the right people, so that when a good raider is looking for a place to hang their hat, you can make sure they find you.