To-Do lists are essential to my life. Without them I lose track of not just time but relative importance as well. I tend to be clearer minded in the morning as opposed to later in the day so I need to make my list early on before other things pop up and distract me (happens at work all the time). It doesn't have to be long - just efficient. I even plan time to goof off a bit or accomplish something enjoyable (like reading a book).
Right now I have Any.Do and Wunderlist on my phone. I use Any.Do for more general, day to day things that are just my problem. It is very quick to add and subtract from and organizes tasks very basic ways.

