The advice I got when I went clipless (surely, from here) was to practice clipping & unclipping while leaning against a wall--both sides, please. Then try it on some grass. Then I did a few laps around the neighborhood. Once, I did a whole organized ride with one foot clipped out, because there were so many unexperienced riders and children (St. Louis Midnight Ramble). However, I don't advise that--I ended up with blisters :-)
"Well-behaved women seldom make history." --Laurel Thatcher Ulrich
'09 Trek WSD 2.1 with a Brooks B-68 saddle
'11 Trek WSD Madone 5.2 with Brooks B-17