Most are handheld, but some on tripod. If handheld, I try to keep shutter speed to no less than 1/100s or so, but sometimes slower if possible. This keeps ISO down which gives better image quality. And given the opportunity, I try to lean against something like a building, lamp post, etc. or place camera on a wall, fence, chair, etc.
I've thought about using a monopod so I can use an even lower shutter speed but haven't done that yet.