How Do You Get Grease Stains Off Of Painted Walls?

The best way to cut grease on painted walls is to use an ammonia solution. To make this mixture, take 1 cup of ammonia and mix it in 8 cups of water. Then dip a sponge in this solution and wipe your walls. Make sure your sponge is not too wet especially if your paint finish is not glossy or wet-proof. This will hopefully remove the grease stains on your wall.

If the smell of ammonia bothers you, you could also use 1 cup of vinegar in the same proportion with water instead of ammonia. Both these materials work just fine.

Just a little tip: If you are planning on painting this wall in the near future, get a glossy paint if you do not already have this. This is much easier to clean. You wont also leave behind any scrubbing marks on the wall this way. There are even some washable paints available in the market. These are basically just glossy paints. They are great for use in kitchens where you are more probable to get grease stains. They are also great for bathrooms because the water does not affect them, which means your paint has a longer life.

Good luck!

If the wall is painted with flat paint, then you will not be able to remove the stains because flat paint is porous and not washable.
If this is the case, then you will need to prime the wall with a primer before painting.
Katie01 has given you excellent advice on the type of paint to use. A latex enamel in a semi-gloss base is washable and not porous, so it won't absorb the grease.

Mr.clean magic eraser. This will take most anything off anything. Best invention ever made, especially if you have kids. They are cheap enough too, only a couple of bucks.