In this brief tutorial video someone who is hosting a successful Tweet-up explains that the main thing they did was get the word out via Facebook, Meetup.com, and Twitter.
Some things to consider when hosting a Tweet-up:
PROVIDE NAMETAGS:
If you provide name tags it will make easier to recognize who is there for the tweet-up. You should put the Twitter username in large print. I sat across the table from a Twitter user I’ve followed and interacted with for as long as I have been on Twitter and we did not recognize each other until we got back home and I was reviewing cards I collected from speed networking.
PICK AN ACCESSIBLE LOCATION:
Of course, a centrally located place that is easy to find and well known will help your turnout. You might want a place that has WiFi access. Don’t forget that bars and restaurants want your business and may make special accommodations for the tweet-up.
TRY TO PICK A GOOD DATE:

Try to pick a date for which there is no competition. Give tweeters a reason to remember your tweetup; serving food or having entertainment are a couple plusses. What about having someone sing, play, or possibly some karaoke. Maybe have it at a venue that includes karaoke; a karaoke tweetup.
PUT OUT THE WORD:
As discussed in the video above, put the word out on Facebook, MeetUp.com, and Twitter. Maybe put it on Meetup first and then link to Meetup in a Tweet. Maybe specially invite high profile tweeters and let it be known that they plan on attending.
LET THE MEDIA KNOW:
If the media cooperates, they could well be one of the biggest sources of attendees. A lot of reporters tweet and would have an interest in attending. Maybe you could try to include something newsworthy in your tweetup.
Somebody in the forum of a content syndication service I subscribe too couldn’t see any results in the search engines as the result of a social bookmarking campaign he was/is doing. I made this video in response using Google Analytics to demonstrate that traffic from social bookmarking sites and Twitter could render Google search results irrelevant.
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