All cabinets and shelves should be lined with waterproof contact paper, This will make it easy to clean and prevent damage to the wood.
Some shelves should already be have contact paper on them. Also plastic baskets should be used for any cleaners stored under the sink or in bathrooms to prevent drip and damage to the shelf.
These are available at walmart, costco, target or amazon. Here is an example **Link**
The dollar store will also have these and cleaning caddys available for cheaper.