Purchase some engine degreaser from your local auto parts store. Usually, one can be effective at cleaning the bonnet and the entire engine. You will need access to a hose and water to rinse off the cleaning solution from the engine. The only things you will need are some clean rags or soft microfiber cloth. Open the bonnet and spray the entire underside with engine degreaser. Continue working from top to bottom, spraying the solution onto the top of the engine block. Be sure to get inside all those small openings where grease and dirt can accumulate. Work from the top to the bottom, getting every exposed area of the engine covered in engine degreaser.
With the bonnet and the engine now covered with the engine degreaser, turn on your engine. The heat from the motor is going to help the degreaser to release all those contaminants, as well as burn off any excess water that is left behind when cleaning. Take the hose and turn on the water, begin spraying the hose at the top of the bonnet. Slowly work your way from the top of the bonnet to the bottom. Working from top to bottom will ensure that any debris that does come off will continue to fall down onto areas that are yet to be cleaned, leaving behind a spotless and clean location.
Once you have sprayed the entire bonnet, work your way along the top of the engine. Spray all the components that have degreaser on them. Work at a good pace because as the engine gets hotter, the steam will begin to fill up the area more quickly. Work from the top of the engine to the bottom, making certain all the degreaser has been rinsed away. Now close the bonnet and allow the heat of the engine to burn off all the water. After a few minutes, you can turn off the motor. Leave the bonnet closed, as the heat of the engine, will still be burning off excess water. Wait for the engine to cool before opening the bonnet again.
Now take a cloth or your soft microfiber cloth, begin wiping down any excess water you see on the bonnet. Work from top to bottom like before, removing water spots and any dirt that may have been left behind during the cleaning process. Run the cloth along the engine, getting any remaining water or debris off the block. As the engine appears much cleaner, you will be able to see certain areas much more easily, allowing you to monitor for leaks during the month at a glance now.