Organize Your Office--Simple routines for managing your workspace, by Ronni Eisenberg, has lots of suggestions.
You might get some ideas from Martin Ternouth's method--the detailed description is about 20% of the way down this page:
http://www.edwardtufte.com/bboard/q-and-a-fetch-msg?msg_id=00008c&topic_id=1
I used to avoid Outlook because it seemed so complex and didn't seem to justify the learning curve. But finally I got desperate and got the pdf they sell here at the David Allen site. It was great--helped me learn what I needed to manage my tasks and reminders, and I don't worry about the other bells and whistles, because David Allen has said I don't need to! It relieved the stress. And I'm slowly learning a bit more and customizing it a little.
Checklists have helped me a lot--Eisenberg discusses them a little, and I've developed some for my own work.
Don't get behind on your bookkeeping. You can use just a checkbook, the paper workbooks they sell at office supply stores, or Quicken Home and Business, or QuickBooks (I work with QuickBooks all the time, don't deal with the Microsoft products, but they're out there too.). I'd start out with the checkbook, separate business account. Start with the simplest approach and stay with that until you're forced to go to Quicken or QuickBooks. You could probably stay with Quicken Home and Business for years--I've seen people with pretty active businesses, employees, receivables and payables, run their businesses with just Quicken. When you start using QuickBooks you'll have to spend more time with the bookkeeping, you'll be distracted from your business, and it will be a drain on you. It can be really helpful, but make sure you really need it before you get it. I get my clients from the QuickBooks program, and they've already purchased the software and want to use it, but many times if I could have sat down with them before they bought it, we could have worked out a simpler, less expensive system for them, especially if no inventory is involved.
And most of all, see a CPA before you start doing payroll. If you're a sole proprietor or a partner, you can't pay yourself payroll and withhold payroll taxes. It can cause you a lot of problems if you do it. Going back and correcting mistakes is not just as expensive as it would have been to do it right from the beginning--it's at least four or five times as expensive, when you add in the penalties and interest you'll pay the IRS and other tax agencies.
Good luck with your business.