Probably the hardest thing about running a guild is turnover. How to minimise churn is another post entirely, but every guild has churn, natural lulls in activity and morale, and the only way to deal with it is to recruit. So, what are some of the more effective ways to recruit?
If your trade is anything like my trade, it is full of trolls and people LFG and general spam. I actually have a separate window for trade spam that is tabbed behind my gchat window. Trade chat advertising has a reputation, I am unsure why, of being beneath serious raiding guilds. If you have a solid recruitment process to weed idiots out, then this should not be an issue for you and a carefully worded 255 character ad placed in trade every so often will drive traffic to your website and your application process.
Yes, you might have a higher turnover of idiots but there are diamonds in that rough, including new transfers (either people with alts on the server looking or just plain random server transfers) or people from guilds already running who are not happy there.
Having a posts here means you can get into more detail about your guild, what you are after and basically pimp yourselves a bit more. I recommend an officer or the guild leader post the thread so that the initial inquiries and checks are of that person. Transfers may dismiss or question a recruitment thread posted by someone other than an officer. Make sure your guild members are aware of the thread and get them actively bumping it and updating it. The WoW forums show how many views there are of a thread, the more view you get, the more people will view it. So, get your guildies bumping up those views as much as they can. Standard rules for trolls apply. Remember, this thread is an ad for your guild, and the way you deal with trolling is indicative of the type of people who think you are cool.
There are several places your threads can go: Your realm's forum, the recruitment forums (horde or alliance), oceanic realm forums. These links are to the US forums. I am an Aussie, so they are the ones I am familiar with. Anyone on EU forums, this applies to you as well, but just on your forums. Go look for places that are relevant but perhaps not immediately on the top of your mind for recruitment threads.
Often the websites keeping track of progression will allow guilds to have recruitment on their guilds. A good example is on wowprogress.com. Find your guild on there and update your recruitment regularly. EJ also has a recruitment section on their forums, and this may suit you as well.
The front public face of your website is the first place people will probably be coming to see your guild. I cannot recommend enough to keep this updated and indicative of the culture of your guild (whatever you choose that to be). Have a recruitment section on the front page with information on the classes you are recruiting. Put up your current progression on the front page as well, and if you are into that sort of thing, victory screenshots! And keep it current and updated. Something with a date on it so people can see immediately that the site is active and the information is up to date. Make the application process immediately obvious and clear for anyone new coming to the site.
Getting up a second 10/25 run with alts is fun, but not everyone's cup of tea. If you have people interested in gearing up and playing alts, then organising a guild alt run is a great way to suss out new recruits. Fill your alt run with pugs, and run it the way you would your main raids. If you find anyone who is decent then encourage them to apply on their mains. You may also find that mains from other guild who come along on an alt may like the way you run your raids better than their own, and you may be able to poach some disgruntled players from other guilds. Specifically running an alt run as a recuitment tool is something you need to start the raid with as a goal.
Word of mouth/friends of friends
Ultimately, the best way you are going to get people is by your reputation and word of mouth. So make sure your reputation is one you approve of. Ask people about your reputation in your application process, find out why they are applying to you and how they found out to apply. Ask your guild mates to be on the lookout for people who would be appropriate for your guild, and to talk to people.
Encourage guild members to be active in recruitment. Recruiting is a hard job and quite demoralising for officers. If everyone in the guild took part and was active, the pressure is off the officers to keep the stiff upper lip. Also, more diversity in recruiting can only be a good thing. Just make sure that your guildies are not recruiting in a way you disapprove of - give them some guidelines to be running with, if you don't want them posting in the forum thread, say so. If you are not happy with trade chat, then tell people so, but also give them something they can do as well.