Most of your queries may be answered in the official step by step guide.
Things to remember: Port forward the correct ports used by the game to your local IP (just opening all ports in your firewall won't direct the internet traffic correctly). They are listed under the "Configuring your Firewall and Router" section of the guide above. There may be occasions when your ISP blocks certain Steam traffic which will makes things difficult. Also note, a dedicated server is meant to run on a separate PC than what you are playing the game. There are workarounds for this (including installing loopback drivers for your network adapter) but it is not the ideal setup for the dedicated server.
Video tutorials I found that may help you setup your server: