Are you are looking for a program of structured practices that will improve your computer skills? Maybe you just want to learn how to use Mail better. One thing to get you started in a program to improve your computer skills is to create a list of the applications you want to master as well as the uses you want to put those applications to, such as how to use Numbers to create and manage (blank), how to organize incoming email to quickly identify priority items, how to work with Pages and Mail to handle things like mail merge, or the easiest way to create presentations with Keynote that really make a difference.
This isn't as daunting as you might think. But as you might suspect, unless you have a program in place to practice by, learning how to use a Mac efficiently can take a very long time of hit and miss effort. The one thing you must be aware of, though, is that unless you apply yourself daily - just like going to the gym to get toned - the results will be sketchy at best.
The same kind of skill-building technique for learning how to type is needed for developing computer skills: a structured program plus daily practice.
It does help to introduce new ideas sequentially rather than all at once. Each new skill requires a few days of practice before adding a new concept.
I recommend two ways to learn using a Mac or an application. One is to get a book that shows all the steps in easy to follow, progressive lessons. The other is to get a set of videos that does the same thing. Quite often, for some very technical processes, a book is not the best choice because it might say something like, "Do A, B, and C to get the desired results." A video does a much better job of showing how that is done. But to master anything takes daily, repetitive practice.
Tutorials abound on the Internet in both text and video format, and don't forget the Forums where people pose questions and get answers. The problem with many video tutorials is that they focus on one aspect of an entire application and are less than 5 minutes, which helps only if that one process is what you are interested in learning about. Still, seeking out all the tutorials and following them through is by far the cheapest way to learn something, but you have to provide the structure and the practice discipline. In this way you are following in the footsteps of people who have been there and done that.
An interesting fact is that even if someone thinks they know the basics of using a mouse, I usually show them a thing or two about using a mouse that they never knew. For instance, a two button mouse (left and right buttons and maybe with a scroll wheel in the middle) has four functions that can be used in every application. Do you know what they are? What can the left button do? What can the right button do? These operations are at the very core of using a computer.
Let me tell you how I learned to work with computers. I bought six books all on the same subject and all by different authors. I studied them one at a time. I applied daily what I was learning just by tinkering with each new idea. Much of the same information was repeated in each book, and each book had something that the others didn't have. After the sixth book was put down, I realized I knew more, with practical experience, than most graduate students. In fact, I met the author of one of the books and discovered he didn't even know everything that was in his book because his students were mostly responsible for the contents.
The point is, learn everything that is offered, even if you don't think you'll use it. It helps to develop a sense of analyzing a situation and seeing how different tools may be used to complete the same task. You probably do this already with some task that you do around the house or at work. Learning a Mac application is really no different.
What I tell everyone is that every application has at least three ways of accomplishing the same thing. Your efficiency with any application is enhanced only after you learn all of them.
I'm not going to mislead you. Using a mentor like myself can be very rewarding, but can also take a very long time. One hour isn't going to get it done. Students spend 40 hours in a classroom environment, learn hundreds of skill building techniques, and within a month of leaving the classroom forget 90% of what they learned - because they don't use it.