Wood is hygroscopic - it wants to achieve moisture equilibrium with its environment. In a humid environment it will take on moisture, while in a dry environment the piece will lose water. Both scenarios may potentially change the shape and create cracks or distortions.
Wood also reacts to sunlight and heat over time by bleaching and shrinking, so It is important to show your piece some love and care.
Dust: use a dry, lint-free cloth.
Clean: remove any accidental splashes as swiftly as possible with a dry, lint-free cloth
Wax: Re-waxing will restore moisture in the grain. Beeswax is plentiful, cheap and ideal. Put a smear on a lint-free cloth (I should start selling lint-free cloths) and work it around and into the surface of the wood. Add another smear if required. allow to dry and buff to your desired sheen.
Oil: Re-oiling will retain freshness and restore moisture in the grain. Mineral oil is perfect - apply in multiple, thin coats rather than one, all-at-once coat. Spread with a lint-free cloth or paper towel and allow complete absorption overnight before applying any further coats. Mineral oil will never dry, so any excess must be wiped off.
Wash: Hand wash a bowl or platter immediately after use. Avoid soaking in water. Use a soapy sponge and a generous rinse. Do not wash in a dishwasher.
Do not use olive oil - there is a risk it may become rancid and odorous.
Please anticipate that the colour and texture of your wood will evolve over time. This is an inherent part of using natural materials.