Engaging your senses can help you become more aware, which will help you on your path to mindfulness.
You can do this in many, many ways, the key is to be fully aware of what sense is being heightened. You could try;

Giving a loved one a hug
Interacting with a pet
Smelling a flower
Notice the feeling of clothing on your skin
Run your tongue through your mouth, what can you taste?
Feel your breath moving
Rub your hands and notice the heat
Listen for sounds in the room and then outside the room.

If your mind and body feel really out of line, then do something bigger such as swimming, going for a run, or touching something really cold to give yourself a jolt back into your body and out of your head. Personally, I love swimming in the sea as I feel I am not only at one with nature (which puts me back into line with myself), but as I dodge waves and try to keep afloat I am hyper aware yet still relaxed.