If your after razors, make sure you have a nice big pair of wellies, plenty of salt, and plenty of time and patience. The BBC have a good tide online, which will, if not for your immediate area at least give you a rough idea of when to start. High and low tides are roughly twelve and a half hours in their cycles, meaning that once low tide has happened, you'll have to wait about 12.5 hours till the next one.
Unfortunately the only razor clam holes I've found, was when I didn't have any salt with me, and the time I did have salt, after much searching over about 5 miles of various parts of the coast line, I found nothing, and it was at completely low tide. I live in hope, as some of the shells that have been washed up have been monsters, over a foot long and around an inch and a half wide. Having said that, these monster razors are unlikely to be found by the casual forager, as smaller, younger ones are the ones you tend to find at low tide, with the larger maturer ones living farther out, deeper.
You could ask around at your local fish mongers and the likes, but make sure you make it clear you only want to find a few for yourself and not set up a commercial prospect, as that may ruffle a few feathers. Perhaps ask a Harbour Master, if you can find them, or local shore fishers may know of a few spots.
While you're out on the shore, why not see if you can grab some other shell fish, like clams, cockles, muscles or limpets? Try sea weed too, there are many types that can be used for eating, although reports of their tastiness vary of course. Gutweed, the slimy green stuff that looks well, like guts, is meant to be nice enough when dried and then deep fried, like crispy sea weed. Dulse can be deep fried to make crisp like things.
I've yet to try sea weeds, but thanks to The River Cottages, 5th handbook, The Edible Seashore has some lovely recipes and good tips etc for all sort of things on the shore, as well as explaining the complex access laws for the shore forager - which as it turns out for those of you not in Scotland, is very very complicated as there is no right of access to the shore in England, it is all owned by someone. Having said that there is work in progress to open it up a bit, but as to when that will happen, I cannot say.
Regardless, good luck and have fun.