Verb

I wish I could find my previous answers on this same question.  I'm sure I've done so at least twice. 

Think of a longer word or phrase to replace in or on.  Use inside of or on top of and that will help you figure out which one you want to use. 

I can ride inside of the taxi.  I took a ride on top of the double decker bus.  She shopped inside of the store.  He ran on top of the field.