Becareful Of Board That Has No Board Marking
Most of the circuit board in the market has board marking but some do not have have. In this case you have to make your own marking so that you would not install the components the other way round. You can also take a digital camera to take some shots before removing the components. A wrongly installed components could cause the equipment to malfunction and some will explode especially the electrolytic capacitors. Just make sure the board has marking before you begin to work.