We always covered them with coal-tar ointment (ichthyol / ichthammal) for a few minutes. They detached without a problem after that, with nothing more than a subtle hint from the tweezers.

Just breaking out the tweezers and yanking away was most emphatically not recommended. It can leave the mouth parts behind, if nothing else.

On dogs my friend likes to strike a match, touch the extinguished tip to the back of the tick, and then pull it out with tweezers. Seems to work