Since I’ve spent a lot of time doing this, here are some thoughts.
First, try Pill Pockets. We’ve found them to work about 50% of the time. Either the cat loves them or just licks them. Luckily, when our largest cat got sick, she loved them. This saved her a LOT of stress. So, they are worth a try.
If that doesn’t work, you can try the crush-and-mix technique. Mix the powder into their normal food, or into something strongly flavored (like human Salmon or Tuna). This will NOT work for bitter pills, so if you are pilling something like Chlorpheniramine or Metroidazole, don’t bother — both are extremely bitter.
For the bitter stuff, try putting the pill in an empty capsule. We didn’t have any blank capsules on hand, so I emptied something safe (my Vitamin B supplements), put the pill in half of the capsule, and used some Pill Pocket to create a stopper (so the pill won’t fall out).
The bitter-in-capsule doesn’t always work, but don’t despair. Time to move to the Pill Gun. Put the assembled pill/capsule in the gun, place it deep in the throat, and “fire”. This has been working for one of our hard to pill cats.
Sometimes liquids, with a syringe, can be easier. But if you syringe, don’t just squirt it down their throat. You risk sending it down their airways. Instead, squirt between their cheek and gum.
A lot of liquids are flavored, but the flavorings they use are just goofy. Why do they flavor Clavamox like bubble gum — when cats can’t taste sweets? They should be flavoring with something strongly savory.