REMEMBER TO CLOSE!!
If a spirit points to "good bye" let it go. If you want to finish the séance place the planchette on "Good Bye" and say that you are now leaving. Everyone should then remove their hands from the board and the table. The board will be closed.
Once you open the gate, you have to close it or entities will continue to float around in an undeterred manner. A simple web search on 'banishing rituals' should provide you with a primer on what to do in order to secure your environment a little better.
Limit the experience to 3 hours a week or else you'll become an addict and consequently a slave to certain spirits.
Cast the Circle before the session and close it afterwards. If you're Christian, keep a rosary close at hand.
NEVER leave the planchette (message indicator) on the board if you aren't using it.
If the planchette goes to the four corners of the board or repeatedly makes a figure eight, it means you have contacted an evil spirit. In these cases, quickly turn the planchette upside down and use it that way.
If you feel anything threatening say goodbye and put the board up immediately.
If you ever want to get rid of your board, DO NOT BURN IT! Break it into seven pieces, sprinkle it with Holy/Consecrated Water then bury it.