The first few times, think about unclipping BEFORE you stop but be prepared to lean towards that side so you don't flip over to the other side. I'd say unclip a good 5 seconds before you have to stop.
Also, adjust the tension to the LOWEST. Coast with the foot you intend to clip out at 6 o'clock (straight down). When you're at the light, back pedal the other foot so it's a little bit pass 12 o'clock so that you can get the most torque to push off with when you start again, then when you're rolling, clip the other foot back in.
With LOOK and road shoes, I'd be really careful cause the bottom of the shoes, the cleats, and the pedals are slick, if you miss and push your foot down, you can risk sliding off the pedal and slamming yourself down.
When you're clipping back in, don't mash down, with the pedal pointed forward, try to gently slide your cleat in like you're sliding into a pair of slippers. The front has a tab that should catch, when you feel that catch, push down to clip back in.