My humidifier has instructions to place it on a hard surface only, not on carpet. Dunno why that is, but my room is carpeted so I put the humidifier up on a table. The instructions also say to keep it a foot away from an exterior wall - I think that's to prevent condensation from building up on the wall and causing water damage.

What kind is it? Is it the kind that uses a fan to evaporate moisture from cold water, or the kind that boils water to create steam? If it's the steam kind, I'd be really careful to put it where you're not going to accidentally kick it over or trip on the cord and knock it over. If there are any little kids in the house, you need to put it up out of reach.