If my assignment was Earth, and I'm assuming you as head of Starfleet are assigning me this planet as opposed to a quadrant the first things I would do is:
1. Get Dr. McCoy to come down and show the earth doctors how to cure the major diseases of our time such as cancer, Parkinson's, heart disease, Alzheimer's, so no one ever loses a loved one, a parent or a child to illness.
If we never develop these things for ourselves our drive to create will be seriously hampered. Why do any work when the magic starship in the sky will do it for you?
2. Get Engineering to get onto making emergency replicators to major areas of poverty and begin to feed the hungry.
You're more than likely to have multiple governments object. Are you going to overthrow governments while your at it?
3. Get Weapons Control to disable all earth weapons with magnetic pulses so there will be no more killing.
Also, you'd more than likely fry every electronic device on the planet.
4. Environmental Staff to assess the physical condtion of planet Earth and ask them to repair and replenish any damaged systems.
People need to have the will to do these things themselves or they mean nothing.
5. Get Spock down there to organize a meeting of world leaders and teach them some logic.
Spock would've already relieved you of command by this point.
6. Lock photon torpedos on and blow up Fox News.
Way to turn a second rate news organization into a martyr... creating further division on the planet.