I have done what you are looking for and I have some advice. I think rather than start off trying to get bylaws and all that stuff going start working on getting your parents interested, have like an informal group for a while, you will need to get a EIN number so your group can open a checking account but you really don't need to worry about all of that other stuff, until you get more formalize have your principal over see eveything with a couple of parents.
We actually went this way for almost seven months before we got our EIN and then a year later we did the bylaws, and did our 501 status. Your top goal right now should be raising awareness about your goals and missions, raising parent involvement.
My recommendations would be:
1-Write a letter going home stating the desire to start a PTO, don't make it a one time thing, use the school newsletter, see if classroom teachers would put something in their weekly updates, posters, talk it up...set that meeting date.
2-First meeting should be a laid back approach, listen to each other, throw around ideas, make a suggestion to name your group at your next meeting...send home followup info!!! Your principal should be running this meeting, you want it to appear that the school supports this and that you were not just handed this...working as a team shows a huge picture.
3-Second meeting, name your group, develop a logo, have parents volunteer to do little jobs, start small...you can't build Rome in a day. Don't plan alot for your first year, a few little things, don't take on a major project...not yet!
4-If it seems you have interest get a EIN number, if you dont have any funds you can wait to open an account, you may need to decide how to get some funds to start, but make sure you are doing a family oriented event as well...don't just ask for money!!!
From there things should get rolling, I find it hard when groups want to start off setting their bylaws before they even have a mission or people involved. The key is that your principal shows support, that way no one can get on a huge power trip. After a year then go for the bylaws, 501 and all that. It takes alot of work to do all of that and it is in your best interest to work on having some fun first!!
As I look back I would still do it this way, I can't imagine sitting with 20 parents for the very first time and saying we need to do bylaws...I would have ran and I think you would find that alot of parents would, they at first are testing the water, seeing if they want to help, if it will be fun, if they are getting into a negative situation. Have Fun with it and take your time, until you really formalize your group you can learn from here and take notes!