Don't pay too much for them. Most people pick thier own, don't let people charge you an arm and a leg for them. Take them in a comfortable, familiar, relaxed environment, with familiar people you're comfortable and relaxed around. Have music playing. If you smoke weed, have some on hand for the come down. Have a bottle of orange juice on hand during the trip. If you start to feel sick drink some. Most importantly, enjoy yourself
If you're gonna be in the woods, wear grungy clothes. You'll want to touch everything, see everything and go everywhere.