Hi Mark
I'm not really experienced enough to give you an informed answer but I can tell you what we do, I'd be very interested to hear if others consider it sensible.
We sail as a family in a BRe and beach stops are large part of the appeal for my kids, so here's the drill:
We only consider a beach stop if it's really sheltered with minimal swell, my biggest worries are rocks and getting pushed broadside to the surf so I'm very cautious.
If we're planning to stop overnight I need an evening high tide , but if we're stopping for a swim and an ice cream an hour or so before low tide is ideal as it means we're not stuck for too long.
Assuming all the above I fill up the ballast and then motor slowly in, keeping a look out for rocks as best we can.
Assuming the beach is shelving nicely I drop the anchor 20 or 30 metres off shore, take down the sails and take up the centreboard and rudder.
We then pay the anchor out as I motor slowly in, looking for rocks all the way.
We put the outboard in neutral and one of us drops over the side (in tevas) when it's around waist deep. Whoever is left in the boat pays out the anchor while the other walks the boat in, feeling for rocks with their feet.
At this point we'll probably decide against it about 30% of the time, get back in the boat and pull ourselves out on the anchor before starting the motor and trying somewhere else. But hopefully we'll decide we've found a suitable spot, pull up the motor and beach the boat.
When we've pulled the boat up we let the tide run out a little and then let out the ballast. This makes a surprising difference to how long you'll have to wait to float off when the tide comes back up again.
We seem to have got away with it so far, but I've only tried it in conditions that seem forgiving and in weather where we're happy to get a bit wet.
Interested to hear how other people go about it.