Every time I try to chat with a host, nothing happens. Why?

1. Generally it's b/c they aren't in front of their computer. Some people leave LW running whilst they're at work, school or asleep or hidden in the background whilst they do other things on the comp.
2. They might not have chat enabled.
3. They might not want to chat or chat at that time.

How do I enable chat so I can chat with a host?

Go to Tools>Options>Chat & tick the option to chat & press Apply. You can also view other people who have chat enabled by right-clicking on the top of the columns & choose show chat. More of an idea can be obtained from here: 1. How do you receive a chat message in Limewire?, 2. Setting Chat up, 3. How to use Bitzi Web Lookup ... & How to use Magnet Links & Direct Connect/Chat

when you see the little smile icon for the chat that means a fellow user is on when you are and is willing to chat. depending if they have it set to chat in their settings.

Yep the chat icon means they have chat enabled & are online at that time. Remember also it's easier to browse those that have the chat icon enabled, be it those from your monitor-upld window or downld window or search results. It's easier to browse from the downld window than the search results when you are downlding from them.