A couple of tips I worked out when I wanted to get used to some new and quite different clipless pedals (Speedplay Zeros) that came on my new road bike.
1) find a quite area to practice in e.g. a quiet empty car park. I'd like to suggest an empty grassed area, to make it softer if you fall over, however pedalling on grass would probably make getting used to clipless harder. A bowling green might do the job, but I doubt they'd be happy when you gouge their playing field when you fall over
2) Start by wearing a regular shoe (e.g. sneaker) on one foot, and your clipless shoe on the other. The best foot to start with for the clipless shoe is the foot that you don't normally put on the ground when you come to a stop on your bike e.g. I'm right handed, so when I come to a stop e.g. at a stop sign, I put my left foot on the ground and leave my right foot on the right pedal. That means I'd initially have the regular shoe on my left foot.
3) Practice riding with your clipless shoe in the pedal to get a feel for it. Practice putting your shoe into the pedal, and removing it. Do that just while riding, as well as when (i.e. before) you're coming to a stop. Be aware that while you're practising this side, it'll actually be less used - your normal shoe foot is the one you'll be clipping in and out with the most. The reason to pick this order first is that you're likely to automatically put that foot down at this point, without the habit of unclipping, which is why this foot has the normal shoe on it.
4) When you've put in a fair bit of practice with that order of normal show / clipless shoe, swap them and do the same again i.e. e.g. go from left-normal/right-clipless to left-clipless/right-normal. This time round it's closer to the way you'll normally ride, as your clipless foot is your favoured "ground" foot. Hopefully in step 3 you've got a lot more comfortable with how the clipless pedal/shoe works, and when you need to unclip before coming to a stop, so it'll make up for the fact that this time round you'll be either having to unclip when you stop, or trying to unnaturally use your unfavoured "ground" foot to stop you falling over. As before, practice clipping, unclipping and coming to a stop.
5) When you've practiced a fair bit on both sides, and are comfortable with the clipless action, and how to come to a stop, making sure you remove your favoured ground foot before you stop, you can then abandon the normal shoes and go fully clipless. Practice with both shoes in clipless, getting used to that. While you might be comfortable with each side being clipless you still need to then become comfortable with both sides being clipless.
At that point you should be able to go for a normal ride, fully clipless, and hopefully you won't fall over. Still be careful though, it can take a reasonable amount of time for dealing with clipless shoes/pedals to become habit. Up until that point, keep reminding yourself that as you're coming towards a stop (and nearly all of the time you know you're going to), that you'll need to get your shoe out of the pedal. It doesn't matter if you do it too early, it just means you're prepared to come to a stop a bit before you need to. The other way round though is a big problem ... leaving it too late is probably the definition of not getting your foot out of the pedal in time and falling over.