Cube up the butter needed for the recipe in tablespoons or smaller and let sit out at room temperature for 30 minutes (may take longer depending on the temperature in your kitchen).
Method #2: Microwave (no water)
Place your stick of butter on a microwave safe plate. Microwave for 30 seconds at 20% butter. Flip over and repeat. (may need to repeat 1-2 more times).
Method #3: Microwave (with water)
Heat a microwave safe cup of water for 2-3 minutes. Place butter on a plate next to it. Keep microwave door closed for 10 minutes to let butter soften.
Method #4: Food Grater
Use a food box grater, grate the butter. Let the butter pieces sit out at room temperature until softened.
I've tried using my stand mixer to soften it by letting the paddle attachment "smash" it and then letting it sit to soften, but if you have a glass bowl be careful I have heard of some people's bowls breaking so I no longer use this method.