You could of course get a big fancy but most of all expensive Black Berry or other PDA, but it costs a lot of money plus it takes some time to get to know the device and use it with no pain. What I personally recommend is the software LeaderTasks, let me explain why.
First of all the software is for the biggest part free, no hided, costs, no spam, no bullshit, no nothing. You just go to the site and download it, and if you would like to unlock more features just buy it, it's not even that expensive! But of course you are here for your problems on planning.
Features
Some of the most important and handy features of the software: It has where you can put tasks, appointments etc. in even in a minute precise! When you are afraid you'll forget your appointment, no worry just set the alarm and you can be warned 5, 10 minutes heck even 5 hours before your task, you can set the time!
You can also set and even make your own priorities, you can give them another color, underline them etc. When you need to know an appointment quickly you can run a filter for the thing you search, such as dentist. The interface thereby is extreme customer friendly, no little words unclear appointments everything nice and clear. The tasks for your day can be viewed on a vertical time line which contributes to the overview.
Alltogether you will get an overdelivered program with many, many more features, don't hasytate to take a look at their site and let yourself be surprised with the comfort of this amazing problem. So if you're serious about getting your on to a whole new level be sure to look at here it has definitely worked for me!