The other night, I got an e-mail from a friend who's kicking herself for letting her car registration expire. Her car got towed and impounded, and was damaged in the process. She has now spent nearly $1000 dollars dealing with all the problems. (My first reaction was that the damage to the car was fairly excessive, but she's pretty much out of luck since it was her fault in the first place by letting her registration expire. D.C.'s great like that.) She freely admits that she was in the wrong here and should have paid more attention to when her registration expired.
What likely happened was that she was expecting to get a bill in the mail and nothing ever appeared. I know that in previous years, I didn't even think about my car registration until the bill appeared. Then I knew it was time to take care of it. This year, I'm prepared and expecting the bill soon, as my registration expires in September. If I don't see something by mid-August, I will be making some phone calls.
My friend could have avoided her problem by simply writing the date in a planner and making a note to check the status of her registration about a month or so before the expiration. There are many options for planners - you can go the paper route, you can have a handheld device, you can have a calendar on your computer, or one online. There are probably others options as well. I've tried them all and always come back to the paper method, but that's just me. A lot of the online calendar services will send you reminders by text or e-mail, which is great for people who forget to check their planners.
A lot of people just pay their bills when prompted. I get an e-mail when my cell phone bill is due. Other bills arrive in the mail. For the most part, I know when these are coming, so I recognize when they're late, but if my life suddenly got busy, it would be very easy to not realize that my credit card bill never appeared and needs to be paid immediately. And missing a bill just leads to added expenses - late fees or worse - service shutoff. Or damage to your car from a negligent towing company.
So save yourself those added expenses. Get a planner. Make a spreadsheet. Check out the calendar option on your computer. Check out an online service like Google Calendar or Remember The Milk. Don't let yourself forget a bill and then regret it later.