If it's a drop in sink with a rim (ie the hole in countertop is smaller than outer dimension of the sink), first disconnect plumbing. Drain and supply lines.
Use a utility knife with a long sharp blade to slide under edge. Work all the way around on at least 3 sides. Wall side may be impossible. Typically sealed with silicone. Then maybe a putty knife to get a little further in. A partner should try to push up from inside cabinet until seal is broken. Should be pushed up and then lifted up evenly on all sides to avoid damage to surrounding tile by tilting.