I have to disagree here. It's always best to go in with a sitter for your first time. Even if there's a 90% chance everything goes perfectly well, there's always the chance things will get weird. Not to mention, you can't trust your sober mind to know how your mind's going to work on an eighth of mushrooms if you haven't tried them before. It's just a completely different headspace, and it's always safer to tread carefully when you start out.
I think many people would disagree with me but I'm glad I got to explore the experience with out any intermediary trying to keep my chill. I've certainly baby sat people who seemed like they needed a minder but I wonder if they would have had a more open and honest trip without someone trying to keep them grounded.
I don't disagree that solo trips can be very beneficial--my most insightful trips have always been on my own. I just think people shouldn't do it alone their first time.