When creating a guild ad ask yourself what information you would want to see as player without that you as player have to do anything else to obtain that information.
For example "We are an awesome guild, more info in game!" is a terrible way to attract more players. In game you don't have nearly the same opportunity as on the forum to explain what your guild is all about and why a player should join it. If I were to read "more info in game" I would already disregard that guild as a viable choice because they didn't find it necessary to explain the guild to me in detail.
A guild is a player association for mutual benefit. Explain in your post what benefits a player will receive when joining and at the same time explain what is expected of the player in order to assist with providing those benefits to all guild members.
Let people know in what time zone your guilds prime time is and whether there are any people online during off-times.
Mention whether you have voice comms and whether voice comms are mandatory, or perhaps only mandatory for PvP. In my own online gaming experience mandatory voice comms make for a better guild as you get players who are truly committed to spending time with the guild while in game.
Mention what your policy on multiple guild memberships is and whether players need to disclose additional guild memberships.
Explain what kind of guild it is (i.e. hardcore wvw, mature, casual). You definitely don't want a player who only plays when he is drunk and uses colorful language as a norm if you are running a family friendly PG guild. Likewise you don't want someone who is easily offended if your guild is named Southpark goes GW2. Make sure people know ahead of time what kind of environment they are joining.
Those are just some suggestions as to what info to include when making a recruitment post. It's obviously up to you whether you use any or all of them.
