I clean as I see it. I may take the whole fridge apart about twice a year. Otherwise if I see a spill, I get a warm sponge with a scratchy side and wipe up anything I see on the shelf. My biggest bugaboo are the door shelves. I try to stay on top of it so that it is not a big job.
For the freezer, the same treatment. Wipe it up as soon as the spill happens. Last month by the end of the month, all I had in there were the nuts and chips for cookies. They were on the door shelf. The freezer got a thorough cleaning before I went shopping.
For the outside, I use oven cleaner. Spray, wipe off. Makes the outside bright, white and new looking.
For the inside, just soap and water. They spills are not there long enough to harden, thus difficult to remove.
Even Spike will grab the spong when he is putting away my groceries.
Now the cabinet where I keep all the can goods, spices, etc. Don't even ask. I keep telling myself I am going to empty the whole thing and give it a good cleaning. Sure I am. Uh huh! I make such a good liar. I do clean the glass on the doors regularly.