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Step 1 would be to know what kind of microcontroller it is so the right tools and the right pins on the chip can be chosen.
In this case the markings of the chip is sanded away. An educated guess can be made by the P2 connector. It's 5 pins which might indicate that it could be a chip from Microchip - if it is a ICSP connector which is not at all certain. It can be anything really.
But since the chip is sanded down due to security-by-obscurity reasons there's a very good chance that they have also set the code-protection bit in the chips configuration registers. Then you can't read out the data or change the programming without fully erasing the entire chip first.
(ok, it might be possible to read it if you have a big wad of $$$ to give some shady Chinese hi-tech company that will open up the chip and use some cool and very expensive equipment to read the data on the die directly.)
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