I have ~5 bikes. I keep a stocked toolbag on each one so they are ready to roll with tubes, patchkits, hex wrenches, sunscreen and whatever other tools are appropriate for that bike. In my pockets go my wallet and cell phone and a utility knife (usually a Leatherman) with keys on it.

That way I can go into the garage intending to ride bike #1 , change my mind and grab #2 and not get any surprises later.

Ben