I'm involved at almost every level possible. My kids go to a Charter Montessori that is actually a conversion from pirvate to charter. It was my idea/influence to actually become a charter. Since our charter, I have been way more involved than I ever was when we were private. I think we have alot of parents that believe I'm actually employed by our school.
I did the PTO for our first two years. This year I'm taking a break from that, but have been on the committee that is designing, ordering, coordinating our new playground. I also spent the first week of school helping to plant some 500 plants. We have a new building and code required specific landscaping before we could move in.
I work part time this year, but I manage to get into the school at least 2 times a week, and spend most of my time there on Fridays, which I have off.
The best way to be involved is to be at school, keep your ears open, be willing to help with just about anything, and stay informed.
BTW, PTO always seem to take such a bad rep. On our board, the age ranges were 25-45, organic vegan to beef lover, SAHM to attorney. PTO's are about the children, and if your PTO operates under that principal, you won't have any problems. And you can drive an SUV, have your nails done and your hair colored, and still be an AP mom and accepting of life styles that may differ from yours.
However you choose to do it, BE INVOLVED!! My kids excel at school, and I know that part of that is due to the fact that I am involved and I do know what is going on. The teachers are my friends...we actually socialize outside of school. So go for it and I hope you love every moment of it!!!!!!!!!