To contact someone about a trip, first use the information they include in the post. You can also send them an email by following these steps. (It does require you to be logged into your account. You can create one by clicking the Join link in the top right of any page.)
- Click on the user name above their picture to view their profile.
- Click the "Send xxx a private message" link on the right sidebar.
- Type your subject, message and click the Post button.
There is a Contact button above each post, but for some reason it doesn't appear to be working now. I will look into this when I have time.