I recently wrote a post in my coven about this, and I believe that alcohol can be used in moderation, but the key to using it is to know your own limits and to know what effect a certain amount is going to have on you.
Alcohol can make meditation a little easier to sink into, however it is a cheating method really and I believe that hard work is much more valuable. Getting into these states by yourself is going to be very beneficial to your development of these abilities. Relying on something to help you is lazy in my opinion.
I usually only do it when I feel very stressed and there is a lot of tension in mind and body and i need a little something to help wind down a little more (or I've been drinking earlier on and happen to have the feeling to meditate).
As for drugs, that is too controversial a topic to go into on a site which children could get the wrong impression.