I've got several of these in my garage:

Closet Pro 10 in. x 3/4 in. White Shelf and Rod Bracket-RP-0045-WT - The Home Depot

I put a piece of innertube over the hook to protect my paint. For long term storage, to take up less space I remove one or both wheels, hang them over the bracket, then hang the bike on the hook by the head tube. It's also possible to use these hooks in pairs to hang bikes by the top tube or by the wheels.