It's not hard, in my opinion. But the important thing to remember is that it's better to take too little than too much. And make sure your tool is sharp so you don't crush the nail. If they're really long, start by taking a little off and then repeat it every couple days, just taking a slice off each time. That makes the quick recede.
If they are white nails, then don't clip the pink. If they are black nails I have a trick for those that works in MOST not all cases..
Put your finger on the pad right underneath the nail. Rest the clippers on your finger, don't push down, just rest it. Then clip.
Now, again, this DOES NOT WORK IN ALL CASES. Just some, but it's also trial and error when you are just learning to clip nails. If a nail bleeds have some flour or cornstarch ready to just dab on the nail.
I think every pet owner should know how to, and be able to, clip their own dog/cat's nails if need be. If they prefer someone else to do it (vet or groomer, etc.) thats fine, but every owner should at least know how and be competent at it. I think it is a responsibility of pet ownership. My biggest complaint that owners have about their dogs are their long nails...of course they are long and sharp when they are only being clipped every 6 weeks..they should be clipped every 2 weeks to keep the nails at an ideal length..and very few owners take their dog for nail trims that often, but they could easily do it at home.