Well I've done it a few times as well as acid. Basically, the biggest thing in my opinion, would be your mindset. It isn't alcohol or weed, where you might do those things to relax and take your mind off a bad situation. Usually, hallucinogens are going to exaggerate those thoughts.
Second, make sure you are in a comfortable environment, with a friend or two, and don't have ANY responsibilities to attend to for the rest of the day. Turn your phone off unless you are using it for music.
Lastly, have a good ass time man. Take enough to trip, if you have some really great shrooms that you know are great, take about 2 grams each. If you have some alright ones that you aren't so sure about, take 3-3.5 grams to experience the full trip. Drink some orange juice to wash it down, and be prepared for the time of your life