What is the first thing you check when a session will not connect?

Most connection problems come down to a short list, and everyone's list is ordered differently by
whatever burned them last.

Ours usually starts with: is the server actually running, is the port reachable from where the
viewer sits, and is something in between quietly dropping the connection.

What is on your list, and what order do you work through it in? If you have a check that has saved
you repeatedly, say so, and say why it earns its place.