First; clear your mind and relax. Having some sweet-smelling candles (I suggest lavender) burning and, other then the candle-light, being in the dark may help.
Second; let go of this world. Envision your spiritual form floating away from your physical body to the realm of spirits or a place you feel comfortable. From there, by will, you may end up in a place known as your "Inner Sanctum" or "Personal Grotto" according to preference.
Third; explore. Check out your Sanctum. At first you may only see trees and mountains, or if you're a city person then buildings, but eventually you should start to see creatures. The creatures you see there are your Spirit Guides. Usually you'll see the smaller ones at first. For me it was the Squirrel, Blue Jay, Cardinal, Mantis, and Salamander that I saw first. Now, after so much practice, I am able to see all my Spirit Guides there and when I am unsure of what to do I usually call a council meeting there to decide with them what should be done.
Good luck with this method, and if you need any help just post your question in the forums.