Collies are big dogs and will need proper nail care especially if they are exercised on the grass or very rarely at all. Long nails will affect the gait, and as "working dogs", gait is important in the show and athletic ring as well as at home.
Use the "clipper" type nail cutters, rather than the "guillatine" type for anything but young puppies. White/ clear nails are easier to cut as the "quick" of the nail (the part with the nerve and blood supply) can be more easily identified. Avoid the "pink" areas, and cut into the white areas only. Dark nails (Tri-colored coats) will be more difficult to identify. I use the clipper type nail cutter and "shave" off very thin slices of the nail, while watching the dog's face. when the dog is very squirmy or seems very apprehensive, I stop shaving. Many dog owners use a "Dremmel" (hand held rotary drill bit type device) grinder, but some dogs don't like the sound of the motor. Have some type of styptic (alum) pencil or Topical Hemostat (25% Aluminum chloride) solution on hand to apply to a nail (along with mechanical pressure( which is bleeding.
Show collies are often put under anesthesia to have their nails ground down to the quick. This is a short-term solution which I do not recommend. as the nail will grow back as before and there may be months of spotty bleeding or even infection at the nail bed, as a result. Show collie paws should resemble the petite and manicured "cat paw"; but don't hurt your dog as a result of this cosmitic desire. You can enhance the paw by clipping excess hair from underneath the pads and at the outlines of the toes.