A variation on this technique is not to focus on any particular object, but to keep actively noticing and naming every mental sensation that comes to your head: e.g. within a few seconds, my mind might bounce from the weight on my right buttock, to the feel of my toes against my left thigh, the slightly tense muscle on my right thigh, to the sensation of saliva in my mouth, to the feeling of my lips pressing against each other...

It gets pretty exhausting pretty quickly, though.