Over the years I have read tons of books on time management and they all say the same thing - YOU MUST HAVE A PLANNER. I have also spent hours looking at different planners, calendars, PDAs, and other organizers for time. I have loved some and hated others. After all of that, I finally found what works for me. I have to have the monthly calendar view as well as a weekly/daily view with time slots. I like to be able to see birthdays, anniversaries, appointments, bills that are due, and big things on the monthly view and also like to be able to fill in specific time-oriented things on my weekly/daily view so that I can plug in things I need to get done. Sometimes my day just has the big things and other days I like to plug in everything that I need to do (even shower/get ready, workout, cook, clean, etc).
Here is the planner I am currently using:
Of course everyone is different and some people can remember everything. I don't know how they do it especially the more responsibilities they have. If you are a person who just wants to know when big things are going to happen, you could just post a calendar in your kitchen and write things on it. If you like to have some space for each day to write a list of what is happening and maybe have a little room for a To-Do List, then having the time slot style might not work as well. There are planners that have monthly views and then each week with blank space for the day. Some people prefer to have a ton of space for each day. For that you can get a daily calendar which gives you a page or two for each day.
Whatever method you choose to use, the key is to use it. Write things down and keep your planner handy so you know what things are coming up and where your time is going. It really helps.