Grounding is more than just a meditation, however it works effectively to put you in a nice, clear space that is highly productive. It is a great way to detoxify your system and Psyche and a fabulous way to draw on the earth's energy supply (don't worry, she doesn't mind at all.)
The process of grounding is really quite simple. Having said that, this is the way I ground myself, and there are plenty of other methods. The important thing is to choose what works best for you.
I sit on the ground (usually under a tree if I can find one...not hard in tropical north Queensland) with my hands resting on my lap palms facing up. I imagine energy being drawn into my body through the base chakra (at the point where your bottom meets the earth) and travelling through my body. This light is always red to me. It travels through every microscopic part, ever cell, every molecule and races towards my hands. As this energy reaches the point of my fingertips, I imagine it flowing out through my fingers towards the sky. With this red light energy goes all of the impurities of body and mind and spirit. The appear to me as black flecks similar to ash from a fire. Once I have completed this process (over about 5 minutes or so) I once again imagine energy being drawn up through my base chakra from the earth. This light is green light. It also races around my body completing a repair job on any part of me (physical or spiritual) that might need healing. I don't necessarily ask for particular parts to be healed, although sometimes I notice the energy lingering in different sections of my body. This green energy travels to the finger tips of one hand and out. It then reenters my body through the other hand and then back to the earth through the base chakra. I allow myself to be a conduit between earth and sky for a while (maybe 10 minutes) and then gently request all the "ports" close (base chakra and hands).
This process refreshes me, gives me energy, heals me and comforts me all in one go. I can do it anywhere, anytime. This particular method has helped me in times of great crisis like when I laboured under post natal depression after my first son. This very simple ritual saved my life.