I like to run some water, not a strong spray, around the painted firewall and sides of the engine, use some car wash soap and rag to swipe what i can reach, and then apply some wax right over the wet painted metal and buff out.
Then apply some 303 Protectant to all the plastic and rubber parts I can reach, this also gets buffed out.(make sure no wax or 303 Protectant gets on belts)
I then apply an inexpensive wax to all the metal engine parts I can reach, I have an inline four so even parts of the block and engine mounts are easily accessible.
I also run a strong spray from the inner fins of the radiaor out toward the grill to clean out dust and dirt. This summer for the first time I sprayed some Fantastic cleaner on the outter radiator grill and let sit then sprayed it off.
Finally a bit of grease on the hood hinges and striker parts of the hood release.
Also, it is a good idea to inspect the floor of the trunk, look for moisture and apply a coat of wax. check for any battery leakage around the battery tray, there are some battery mats that help absorb any leakage.