Look for clear patches of water where waves aren’t breaking as these are deeper holes where fish will conceal themselves.

One good way of looking at it is that the places where it is dangerous and you shouldn't swim are the spots to throw a bait in.  Heaps of info on the web about how to recognise rips and channels for swimming dangers.  Any rip going out to sea will normally have a channel leading to it, different spots along the channel and the rip exit make for good fishing.

Another way is to walk the beach at low tide.  You will see long lengths of low areas, these are where the channels are during high tide.  They normally last a few days to a few months.  Draw a line marking each side of the low area up above the high tide mark and head there with the rod a couple of hours before high tide. 

If you wish to fish during low tide or at high tide if you haven't sussed the area out previously, then spotting the difference in wave action is the best way.  The higher you are the better so climb the sand dune and just watch the waves in the area.  For a channel or a hole you will see the waves breaking further out but as they come in closer the break stops and the form a smooth lump before breaking close to the beach again.   The exit of the channel or hole will see an area (think road) heading out to sea where the waves just aren't breaking as much as they are at the rest of the area of the beach.

If there is not much swell and calm waters, the holes and channels can be near impossible to spot.  This is why it is better to suss the beach out when it is rough.   Any hole / channel you discover will fish well for quite a few days to months, but it will eventually start to fill in and shallow up.  Don't worry, another will be forming somewhere else on the beach.

Possible channel marked here since it is a stationary photo.  Seeing the wave movement will highlight it more.  Not all rips have channels but most do:

awesome thanks :)