Tough various items around you: a pen, keys, your clothing, the table, the walls, etc. Notice the textures, materials, colors, weight, temperatures. Compare objects you touch: Is one colder? Lighter?
Dig your feet into the floor: Literally "ground" them! Notice the tension centered in your heels as you do this. Remind yourself that you are connected to the ground
Carry a grounding object in your pocket- a small object (a small rock, clay, a ring, a piece of cloth, etc.) that you can touch or look at whenever you feel triggered
Jump up and down
Notice your body: the weight of your body in the chair; wiggling your toes in your socks; the feel of your back against the chair. You are connected to this world.
Stretch. Extend your fingers, arms, and legs as far as you can reach them
Clench and release your fists
Walk slowly, noticing each footstep, saying "left" or "right" with each step
Eat something, describing the flavor in detail to yourself
Smell something, describing the scent in detail to yourself
Focus on your breathing, noticing each inhale and exhale.