First, remove all knobs and handles, as well as the contents of your cabinets and drawers. Use masking tape to protect hinges and glass and put down dust sheets to protect other parts of the room as necessary.
Wash the cabinets down with sugar soap or a strong detergent solution. This will remove grease and create a smooth surface. Remove soap residue with a damp cloth.
When the cabinets are dry, sand with fine paper (you can skip this step if you have melamine or high gloss surfaces). Fill imperfections with a good quality ready mixed filler and sand again.
Apply a wood or melamine primer depending on the surface. You might want to use a small roller on doors for a smooth finish.
Apply two coats of your chosen colour. After the first coat is completely dry, sand with a fine paper to ensure a smooth, professional finish. Remember to wipe off any dust with a damp cloth.
When the second coat is completely dry, carefully remove the masking tape, put the knobs and handles back on, and admire your sparkling new cabinets.