How do I find out if a user is online so as to initiate a chat?
If you have the user on your buddy list, the username would appear on your Chat Monitor.
You can click on that buddy's name to see their profile,
which also has a link on the top-right hand corner that you can click on to begin a chat.
Another method of starting a chat is to look through who's online and find the user you want to chat with.