This is my generic format for spellcasting and for rituals. It's set up for one person, but could be easily adapted for use in a group setting (for instance, you'd make the circle larger, and would say "WE thank the Goddess" rather than "I thank the Goddess"). Of course, you can change it as you see fit; nothing is cast in stone. It borrows heavily from the writings of Silver RavenWolf, Gerina Dunwich, and Starhawk.
A word of warning: one writer has said that the way magick works is by making everything fall apart. The Deities have a sense of humor. Don't be surprised if you get what you ask for ... but in an unusual container.
Before you do anything else, write out a Statement of Purpose. Make a list of everything that you want to ask for: guidance about your job, healing for a friend's daughter, success in some upcoming endeavor, healing of emotional hurts, accuracy in divination, strength to put up with the jerk you work with at your office, wisdom to make a special decision. This is the "meat" of the session. Be "generally specific," i.e., define the qualities of what you want but leave yourself open as to HOW it will manifest. Remember that you're not giving a grocery list to the deities; you're asking for their help.
Of course, you don't even have to ASK for anything; you can circle to celebrate a Sabbat, or just to "hook up" with the other side.
I usually take a shower just before doing ritual. I then put on comfortable clothing and an amulet, usually a pentagram.
If you aren't sure which way is north, consult a compass. When you set up your altar (and later, when you call the quarters), you'll need to know what direction you're facing.
And I always lock up the household pets, or put them out in the back yard. I don't want them wandering into the circle during ritual. The word "sacred" (as in "sacred space") means SET APART. It's special. Let the animals graze somewhere else.
One more thing: Don't bring a watch into the circle. If there's a clock on the wall, cover it. When you're in sacred space, there is no time.
Then you gather up the materials you're going to use and take them to the place where you'll cast the circle (you may need to move the furniture back). After you've cast a few circles, you'll find yourself keeping most of your equipment in one place (such as a cardboard box). I use: