1. Have an affinity for DIY.
2. Get bored with your current social gathering, stop going.
3. Stew for a few months.
4. Bring a partner in who's also bored so as to toss around some responsibility.
5. Think about places nearby willing to host a gaggle of nerds for free that has adequate space and electricity.
6. Contact your local DIY publications and get their support.
7. Scheme up ways to generate money to support the group's work.
8. Be flexible as far as venues and dates are concerned.
9. Don't schedule a meeting on a party night.
10. Invite everyone.
11. Make a website where interested parties can collaboratively plan, find resources and you can link to event notices.
12. Be enthusiastic.
13. Find people who have equipment or interesting ideas to attend so people don't get bored and you don't have to spend a lot of money.
14. Create an interactive building tutorial so people can learn, be social and create something of their own.
15. Document everything.
16. Post your event notice to relevant websites and mailing lists.
17. Be very friendly and diplomatic.
I never carry a bag, but an umbrella is a must. Here's an interesting way to tote an umbrella.
Clothing with loop
Assuming your umbrella has a long enough hand strap (if not, make one), pull the strap through your beltloop and behind a few of the spokes protruding toward the handle. Then close the handle so it locks. Ta-da!