If you’re a local chapter of a larger organization, ask for help. Your larger organization may have some excellent services to offer.
First: the perfect is the enemy of the good. Do something. Learn from it. Try something else. For the first year or two your online presence will have almost no traffic, so making mistakes won’t hurt your org. But the longer you wait the longer you will be offline.
Second: Register the domain name that will be your online trademark. You’re going to need to fool around looking for a domain that’s available that’s a suitable trademark for you. I like namecheap com as a registrar, because they don’t include a baffling bunch of upselling in their checkout process.
Third: if you’re a local organization with a street address or a local service area or both, figure out how to get your listing on Google Places for Business. This is vital for users of Google to find you. It’s also helpful because the questions you need to answer for your profile will help you focus your strategy. Google serves people who search, and they know what sorts of things people look for.
Fourth: consider setting up a Facebook page. Put a link to it in your Google Places listing. Ask / beg / pester your members and staff to “like” the page. Once you have fifty “Likes” it’s easier to promote and control your page. Ditto for LinkedIn if your org is focused on people in their workplaces. Post interesting things once in a while.
Fifth: Start an online mail list. Both mailchimp.com and madmimi.com offer free service tiers for starting out. Ask / beg / pester people to sign up for your emails. Send them something interesting once every couple of weeks.
Sixth: Set up a web site. When you’re starting out you can get Weebly or WordPress.com to serve your web site with your own domain name for very short money. Here’s what to do in Weebly and WordPress.com. Make sure the front door page (the home page) of your web site tells the world what you do, when you do it, how to find you, and why we should care. People love pictures. Don’t put the words Under Construction on your web site, unless you want search engines to ignore you.
Seventh: revisit your Facebook, Google Places, LinkedIn, and email lists. Make sure they refer correctly to your web site and vice versa.
These things are quite easy to do. Do them! Once you’ve done these things, you can take some time to reflect on how well they’re serving your constituents, and update them as needed.