First if you employer is matching your contribution to your 401K or IRA, put in the percentage they are match (if at all possible). This is found money and will benefit you. If you can put more, I suggest putting more money into your retirement account, after all its tax free.
Flexible spending accounts are great. First review what your plan covers, plans vary a little on what they cover, for example some do cover child care and over the counter medicine, some do not. You can use last years tax return (if you itemize) as a guide to see how much put away. Just remember if you do not use it but the end of the year, you loose it.
If you are active in a charity and will be writing a check for the cause, why not see if your company matches your charitable gift. Many larger companies do. This will help your donation go that much futher.
Look at your company's benefits package. Take advantage of them, they are there for you to use and help you.