If you're having trouble connecting, sometimes the solution is as simple as enabling Passive mode. You can find this option by navigating to File > Manage Servers and putting a checkmark in the box next to Passive Mode.
Pretty nifty, but what exactly does it mean? Well, the answer is a bit technical, and has to deal with these things called ports. A port is an opening on your computer that allows it to exchange data with another computer. When you transfer files to your server, two ports are normally used: 20 and 21. Port 20 sends requests to the server (such as PUT, GET, and PWD), and Port 21 sends actual files, folders, and directory listings to the server.
Like we said, pretty technical. Think of it this way: Your computer calls up the server on Port 20 to say, "Hey, I'm sending out some information. Is that cool?" When the server responds, "Yeah, that's cool," your computer uses Port 21 to send out the actual data in question.
Now, normally when you connect to a server, the server is what establishes the data connection to your computer using Port 20 — basically, it says, "Please start sending data now." But when you use Passive mode, your computer can establish the data connection. That means your computer basically gives your server a heads-up, but doesn't wait for the server to say, "Please start sending data now."
As we said before, passive mode is usually the quickest fix for common connection problems. It may even be required for users who are behind some types of router-based firewalls. However, if you use Passive mode and get a 426 error, disable it. This error means the server does not allow Passive transfers.
For more information than you ever thought existed about Passive mode, read this article.