Tell them roughly how much you are prepared to spend. Look through the recommended binoculars in your price range, and choose the one that gives the best optical image, and feels easiest to use. Using binoculars is simply a matter of practice, so take a while to find out what suits you. The eyecups, which can usually be folded or pushed down, if you wear spectacles. The height of the strap, which is best kept short, so the binoculars sit snugly against your chest.
Field guides Another potentially confusing area is choosing and using a field guide.
Used with your field notebook, to look up birds you cannot identify in the field, after returning home. Fortunately several new guides cover a more limited range of British species in more depth. It's certainly worth paying a pound or two more to get the one that you want. Only by comparing the bird in the field with several different illustrations and descriptions are you likely to be absolutely certain of your identification. And remember, there is no substitute for close observation, and learning by experience.