Hosting a tournament

I decided to host a mini tournament for friends. 8 teams ended up signing up, which was more than I expected. Now that it's coming up I realized i don't quite know how to run it. How exactly do I choose which teams face who? How do I invite everyone into matches and such? How do I keep track of each game going on? Should i make it last all day, like do one team at a time?

Anyone with experience care to give me some insight on how to make it runs smoothly and efficiently? I would greatly appreciate any tips.