I am very fortunate in that I got them used to it as kittens. 3 out of my 5 will allow me to set them on their backs in my lap and I can easily extend claw by pushing on toe pad and snip with pet nail trimmers, the kind that look kind of like scissors but have a guard so you don't cut off too much. The other 2 I have to stand them on a counter and hold one paw up at a time while I have their body snugged up under my arm to keep squirming and moving about at a minimum and I must do those with regular people nail trimmers. If any of them get to antsy I stop. I only trim front claws regularly, back claws rarely need it. My one cat loves to have his front paws touched and massaged and messed around with so he is a dream to trim, I don't even have to hold him, just plop him belly up on my lap and snip snip snip.
Sometimes during petting time if you softly touch paws and massage the paws they will get more used to having you touch them for trimming claws.