That is a big question and even experienced anglers do not always get it right.

A good idea is to go to a beach at the bottom of a Spring tide and take a small notebook with you so that you can make entries concerning sandbars that are going to break the surf and make aerated water where sandeels and worm are going to be washed out of their burrows by the effects of the "washing machine" turbulence caused by the undertow.

Count the number of paces from a path or outcrop of rock so that you can find these sandbars or deeper pools where wave borne turbulence has washed the sand away. No doubt during the summer the kids will be playing in these pools, but in the right conditions this is where fish will be found.

Many rocky outcrops will have a pool washed along one side where the tide has scoured the sand away, make a note about which side of the rock the pool can be found.
Look out for fresh water streams that wend their way across the beach. Bass in particular are known to favour areas where the salinity of the salt water has been diluted by the fresh water.

Look out also for fresh water springs that bubble up, sometimes many yards from the beach. These are always the prime spots for bass, dabs and plaice.

Go up as high as you can on a really calm day, wear a pair of polarised glasses and look for areas of water that are coloured slightly different. These are often fresh water springs bubbling up into the sea and are prime areas to fish.