Make sure the device is switched off and plugged out. If needed, let the device cool down.
Just use a slightly wet sponge to clean, don't use brushes, no sharp cleaning supplies, no cleaning petrol, thinner, alcohol. Dry it with a clean and soft cloth.
Make sure no fluids get into the device.
Use the device only completely dry.
Roll up the cable so it doesn't break.
Keep the device in the original packaging in a clean, cool and dry place.