The ideal implement is a short handled potato fork.
Failing that buy a standard (short handled) fork and take a lump hammer to the tines to flatten them a bit.
The best method is a trench. It depends on the water level how deep you must go, as the lug tend to lie up in the bottom of the U bend. The U bend lies between the squiggles at one end and a single hole at the other. Oddly that single hole will often contain a maddie or small white ragworm (not as often on west coast beaches).
On some beaches the worms will be barely more than a single fork deep. On others, it can be sheer murder. Two even three forks down.
Wear proper
gloves. The sand will rip the s***e off your hands, unless you're a brickie! No fun fishing with cold and abraided hands later...
On very wet beaches, its often a good idea to
dig a shallow trench to drain off the surface water. When you dig the real trench, it will not fill with water.
This will make spotting worms and tubes easier.
When you dig,
drop the clods from waist high. They will fracture along the lines of the empty "tubes" left by the worms, which is also where the worms will be...
One digging and one watching is prefect - you would be amazed how hard they are to spot on your own. You will miss loads.
Damaged worms will spoil and kill whole ones. Keep them separate and use them quickly.
As you dig, follow the tubes down. The means
digging at an angle, not straight down. This is key, especially on deeper beaches and/or when seeking black lug.
It means you can follow the tubes and hunt the worms rather than trusting to blind luck.
Blind luck can be very useful, mind!
After you have dug the first line. dig a second beside it. Throw the sods up and let the fall / crack on the spoil from the first trench. You will find more worms this way.
Throw all the subsequent lines from your trench onto the same spoil "hills". Don't
not try to fill in your last line in a trench. You will miss worms. The first tide will fill it...
A good dig will look like a square when you are finished. So pick an area with lots of big squiggle casts,
fresh casts that have not slumped.
Hope this helps...
K