The Hunter's Mark
has an interesting post regarding making the transition from casual to hardcode raiding for if you decide that you have enough of PuGs or your casual guild and want something a bit more hardcore. Although aimed at WoW
the ideas and concepts are true for all the other games that also have a similar raiding system.
The guide starts off with the important point of checking that your current guild doesn't already have plans for that already, not burning your bridges with your current guild leadership because that may well be asked what you are like by your new guild and then where to go to actually find your new guild. It follows up with actually getting onto your guilds raids if they use DKP or a system like EPGP, how to be prepared through doing your homework and finally how to keep that spot when you get it so that you can continue raiding.