Make sure to include the right hashtag(s) every time you tweet at the event. Most events have at least one officially dedicated event hashtag. Pay attention on Twitter, don't just assume you know what it is. When in doubt, do a quick search to make sure. You might also find some unofficial hashtags that might be popular within the community. If you are tweeting during a speech, feel free to copy the hashtag(s), so that you can just paste it. Speed is a virtue in social media.