Clean the engine bay with an engine degreaser. Use appropriate product depending on the severity of grease/dirt. My engine bay has never been greasy, so I use Simple Green, which works well for me. Caution using water around electrical components. The thing that makes the engine bay pop is what you use as a detailer. I use CD-2 Engine Detailer. This stuff is absolutely amazing. After the engine bay has been cleaned and dried, spray CD-2 liberally all over the engine bay and let sit for an hour or so. Then drive the car for about 20 minutes to set the spray. The result is nothing short of incredible.