For spills: Soak a paper towel in vinegar and place on oven spills for 30+ minutes. (preferably in a warm oven) Wipe off.
Here are a few home made recipes for oven cleaner.
Spray bottle filled with warm water
Spray oven with water
Sprinkle baking soda on the wet areas
For any remaining residue, use a wet sponge (hot water) with a little dish detergent squirted on it.
Mix together in a bowl, 1 tbsp. dish soap, 1 1/2 cups baking soda, 1/4 cup white vinegar. Add water to make a paste.
With a paintbrush, brush paste on the oven and leave overnight.
Wipe clean in the morning.
Warm oven then turn off
Make sure you wear eye protection and rubber gloves. Don't breath in the fumes.
Add 1 – 2 cups of ammonia to oven proof dish and place on middle rack
Fill another dish with 2 cups boiling water and place on bottom rack.
Wipe with a wet sponge in the morning
Note: For oven racks, place them in a garbage bag, add ammonia and seal the bag with a twist tie. Lay flat (preferably outside). Leave for a few hours then wipe off residue.