Begin Where You Are
I filled out a time-management questionnaire recently (see references below), and one question was, "Where should I begin, if I want to keep my appointments better?" The only general-purpose answer to such a question is: begin where you are.
You always must begin from where you are. Always. Whatever the goal. You need to know the "current reality" to figure out the next steps. And the next step always starts where you are and moves toward where you're going. You may "work backwards" from the goal, but you won't find where to begin unless you work backwards all the way to where you are now.
To take the case of keeping appointments — you need to ask, where am I now?
For example, if you don't keep a central calendar, you are starting from zero. Get a calendar and start using it.
On the other hand, if you have a calendar, but you aren't using it regularly, you begin from there. Figure out when to look at it so you don't miss the appointments. First thing in the morning? The night before? What works best for you?
What if it's neither of these? What if you have a calendar and check it regularly, but you're still missing appointments? Then you probably need to investigate to further understand where you are now. What's going wrong? Maybe you need to keep a log to help you identify why you're missing appointments. Once you know the problem, you can solve it. But you can only solve it if you know your starting place, and start from there.
This shows why I teach thinking tactics rather than time management per se. There are many helpful systems for time management (several of which I recommend on my site — see references below). But the key to any of them is the thinking you do to implement them.
Even something as straightforward as using a calendar needs thinking to implement it — thinking about what kind of calendar works for you, about what you will keep on the calendar, about how you will remember to use it. Knowing how other people use a calendar can give you ideas for how to use yours, but ultimately, you need to adapt it to your situation. There is no one-size-fits-all answer to any of these questions.
That's why you begin where you are.
My thoughts on time management are in my Blog post:
What's so hard about managing time?
New: FAQ on Time Management — I gave extensive answers on a survey on the Schedulemailer site:
Book Recommendations on Time Management: