Step 1: Get a dog that you don't have to trim the hair under your dog's paws. There are many good breeds out there for which this is true. If you are unfortunate enough to have chosen the breed of your dog unwisely, follow the remaining steps.
Step 2: Put off trimming the hair until the next weekend.
Step 3: Put off trimming the hair on that weekend too.
Step 4: Repeat steps 2 and 3 until either you feel terribly guilty or until your dogs start limping.
Step 5: Once the step 4 stage is reached, you are ready to begin. To trim the dogs, you will need (a) an electric clipper, (b) a scissors, (c) glasses if you are of a certain age, and (d) a head lamp. A head lamp is basically a flashlight attached to a strap that you place around your head so that your hands are left free. Yes, they exist. You can buy a head lamp at any store that sells outdoor/hiking gear. Go in and ask them for a headlamp for trimming the hair between dogs' paws. This will not help you get the said product, but it will give you the satisfaction of confusing a poor store clerk, and given what you are about to embark on, you should take satisfaction wherever you can get it.
Step 6: Assemble the instruments, yourself, and the dog in one place. This is harder than it looks, especially if you've tried this before and the dog is wise to what you plan to do.
Step 7: Once you have instructed, cajoled, shouted at, and dragged the dog into place, get it to lie down on its side. Depending on the size of the dog, this may be as simple as lifting the small dog and laying it on its side. If, however, you have a 125 lb dog which is capable of dragging a 200 lb person and which therefore has sturdy, muscular legs, you may be in for a bit of a struggle. Pressing on their back will not work - they've got 4 legs and way more stability than you do. And muscular legs.
Step 8: Take a breather every now and then. Now is a good time to remember that you should have been training your dog with the "down" command.
Step 9: If you succeed in getting the dog to lie down, go to step 10. Otherwise go to step 2.
Step 10: Grasp the paw firmly, and use the clipper to trim the hair such that the clipper blade is flat on the paw pad.
Step 11: To trim the hair between the paw pads, use your thumb to separate the pads. Hold the paw firmly, because dogs are ticklish between their paws. Really, and failure to hold the paws firmly will result in clipper being tossed out of your hands onto the floor where it will vibrate in a grating fashion just out of reach when the dog yanks back its paw.
Step 12: Retrieve clipper, make sure the head lamp is lit, and grab the paw again. Ignore the aggrieved look of the dog, there'll be lots of that. Hold very firmly, separate the pads again, and use the clipper to trim between the pads. Now, when I said firmly just now, what I really meant was "with a death grip". Ignore any looks or twisting that the dog is making while you grimly trim the hair. Hold tightly!!
Step 13: Before you start step 12, you might want to consider whether your dog really is loving and obedient to you and the fact that any dog can twist around enough to bite you no matter how you hold their leg.
Step 14: Do NOT under any condition clip the webbing the dogs have between the pads!!! You will either test the dog's love for you, or step 6 will become intolerably difficult in the future. You will definitely end the session for this weekend and putting antiseptic on the paw of a dog who thinks you are about to poke it again is nigh impossible.
Step 15: If you have a very long haired dog with black hair, you will not be able to see where the webbing is until you clip it.
Step 16: After about ten minutes of grim struggle with the dog and determined clipping in murky light (the headlamp usually doesn't work well) you will have clipped the hair under one paw. Congratulations. DO NOT LET THE DOG GET UP!
Step 17: Pet the dog to get calm and to remind yourself that you really do love it.
Step 18: Great! You've got three more paws.
Step 19: Consider step 2, but remember you are made of sterner stuff. Repeat steps 10 to 17 for each remaining paw.
Step 20: When you are done in the next hour and a half, remember that exhausted as you will be, you will need to clean and oil the clipper, sweep up the trimmed hair, and clean the scratch wounds on your arms. Remember also that no matter how guilty you are and how much you wish to make amends, the dog will not want to be your friend for at least 5-6 hours.
Addendum: If you have more than one dog, use the time between clipping each dog's paws to compose the e-mail to your ex explaining reasonably that they were the ones who wanted the damned dogs and they should damned well come over and help you clip the damned hair and that you said you would have been perfectly happy with short haired Dobermen. But make sure that your ex is in another country if you send the e-mail, because the only thing worse than clipping the dogs' paws is having your ex come across to do all three dogs in half hour while giving you advice on how to do it.