Protect yourself from the chance that you will write bad checks.
Keeping track of all your transactions is the easiest and most important thing you can do to manage your checking account. This could be annoying if you have to write a lot of small checks for small things, but it will be worth it in the end. By writing down each check you write and how much it was for, you will know exactly how much money you have to spend, how much you have already spent, and whether or not you can afford what you are buying.
There are many good reasons to keep track of where your money goes. But those aren't the only reasons you should know how to handle your checking account. Let's say you don't know how much money you have in your checking account. It's getting close to the end of the month, so you know you might not have much money left, but you're not sure. So, you write your last check, but it doesn't clear. Bounced checks are embarrassing and will cause you to lose a lot of money for no other reason than that you were careless. First of all, most places will charge you extra fees if your check bounces, and you might not be able to write checks again. Second, most banks have high fees for going overdrawn, which you don't want to waste money on.
If you want to learn how to manage your checking account, the next thing you should do is try to keep a few hundred dollars in your account as a buffer. This isn't just to protect against overdraft fees and checks that don't clear, though. It can also be useful. For instance, it's always possible that there could be an emergency situation in which you need some extra money - in which case having extra dollars in your checking account could be a life saver.
These are the most important things you should do to keep your checking account in good shape. Make sure you have extra money in your account at all times, and keep track of how much you spend.