Okay, I'll start. Applying joint compound? Wanna get it smoooooooth? Ad about 1 teaspoon of dish soap per gallon of compound and it will glide on like butter - a little secret the pro's use. Smells nice too! Also, premixed joint compound is too thick for most applications, and is meant to be watered down. For finish coats, the thinner you're able to manage it the nicer a finish you'll be able to achieve. Don't forget to prime!