I am using the command line wallet, and mining on my PC. The daemon says I have '8+0 connections', which I believe is the default. I believe this means I am connected to 8 nodes, but no one is connected to me. Am I correct in assuming that every block I mine is empty because I am not connected to anyone? Is there a guide that someone could link to to help me open port 18080 to allow others to connect to me? Also, what are the pros and cons for connecting to others? Would it strengthen the network more, increase my orphan rate, give me transaction fees? Is it worth it?
It's tough to write a step by step guide for port forwarding, because port forwarding is something your router does, and people have different routers.
If your router has UPnP, that would be the easiest. Many people will argue that it's safer for UPnP to be off, which is correct; but you can enable it long enough for it to allow the daemon to punch a hole through the firewall (a non-technical term for port forwarding), and then turn it back off. The port forwarding would have been performed automatically in that case.
But anyway, just look at your router's instructions for port forwarding. Nearly all modern routers allow port forwarding, and it is not complicated.
Your other questions can either be asked in separate questions, or they may actually have already been asked and answered, so please search a bit.
When you open up port 18080, you strengthen the network by allowing others to connect to you to download the block chain.
Look at your modem/router and get the exact name, model, as well as your internet provider name. Then "google" with that information on how to do port forwarding. Takes a little bit of effort but it's fairly simple, after you do it one time. The "know how" you need is on the internet.