swampy1970 said:....It's all about practise. If you feel like you're not that quick, just spend some time on a road that gently goes down hill, practising getting that last foot clipped in. Once you've clipped in, unclip and do it again.... and again... and again until you don't have to look (Look... get it? Like the pedals Har har) down to put your feet in.
Good advice, practice and it will become easy.
But the main thing the event organizers are really concerned about is folks causing big pileups as they start because they fumble while clipping in and either swerve all over the place, come to complete stop in their confusion or are so distracted while staring down at their pedals that they run right into another slow, wobbly or stopped rider.
IOW, give yourself a little bit of breathing room when you line up if possible so you're not right on top of the folks in front of you or squeezed in too tightly between other riders. Then get a good solid starting stroke from that left foot so you have some momentum and hopefully some balance which means choosing a decently large starting gear if the terrain is flat. Don't start flat events in your small chainring, you won't be able to get up to a reasonable speed with a tiny gear in half a pedal stroke.
When you practice clipping in make sure you can ride a relatively straight line and look up as much as possible as your foot finds the pedal. Also make sure to keep your hands up on the brake hoods ready to feather the brakes a bit if you start running up on someone who's stopped or struggling to get in.
The last tip is an old time crit trick, but can be useful if you're really struggling. Practice riding a few pedal strokes before you get your right foot clipped in. It's not great and modern road pedals are pretty slippery when ridden upside down so you can't put out full power but you can ride the pedal without being clipped in. If you roll off the start and everyone is getting clipped in faster, don't panic. Just pedal a bit gently for a few more strokes to get the bike up to speed, the bike will handle better and ride a straighter line with speed. Then get clipped in. This used to be standard procedure in the toeclip and strap days and it's still very useful during fast starts or if you have equipment troubles like a bit of mud on your cleats. I've ridden the first lap of fast crits before getting securely in when I had badly worn cleats, it's not great but it beats letting the group simply ride away or being responsible for a big pileup.
Good luck,
-Dave