What order should I centre, ground and shield in?

Opinions on this vary. I think the most common is to ground, centre and then shield. The rationale being that you siphon off your excess energy first then centre and balance the positive energy that remains and then finally focus your energy into creating a protective shield.
I do it a bit differently though. For me, centering is the process of drawing together all the energy I want to return to the earth. So I centre first. I focus my energies into a focal point in my body and then hold it steady for it to be returned into the earth.  Its the part of the process that I find the most difficult as I've never found a visualisation for it that I'm completely happy with (suggestions on a postcard please!) and it usually takes me a lot longer than the grounding which I find the most beneficial.
I do also know of one witch who always shields first and then does all her energy work inside her shield. So I think it is very much what feels right and works best for you.

Image http://browse.deviantart.com/art/Forcefield-Powercard-142642037 (Branganator)

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