I'm planning on putting a bathrobe/extra towel hook on the back of my bathroom door, but I'm pretty sure it's hollow wood. Can I just use the standard screws that come with the hook kit, or do I need something else?
You'll need hollow door fixings - something like these
Expanding wings grip securely in hollow doors, thin skin partitions, plywood and fibreglass. Ideal for the home, boat and caravan.
It sounds like you already purchased a hook, but I can recommend 3M Command products. They use a removable, non-damaging adhesive strip.