My frugal tip of the week is timeliness.
Return library and rental materials on time. Yes, the overdue fee is small but it adds up quick. Many libraries have online systems so you can renew items from home. And remember that it needs to be returned by the time the library closes that day to count.
Pay your bills on time. Mail them at least a week earlier or set up automatic payment. The credit card company doesn't care when you meant to send it...if it is not there on the day...not only do you get a fee but you have to pay finance charges on the balance. I also try to pay bills when I get them in the mail or on payday. Have a designated place for bills in your house so you don't loose or forget about them. Set up automatic payment for all of your regular monthly bills (power, water, cable, mortgage, school loan).
Also, make sure your bank account has money in it. Overdraft fees are incredible and you may not even know you are overdrawn. Each transaction produces a fee. You can also avoid this by getting overdraft protection on your account for a small monthly fee (which is smaller than even 1 overdraft penalty fee). Many banks offer online account information...check your account a couple times per week.