A cover-up is not simply a new tattoo placed over an old one. The artist has to work with the existing darkness, shape, colour and placement. A strong result starts with a realistic read of what is already there.
What makes a good cover-up candidate
Older, faded and smaller tattoos generally offer more room than dense, saturated pieces. The direction of the existing lines matters too: a flexible shape can be absorbed into a larger composition, while a block of solid black may need a darker design or some lightening first.
What to expect from the design process
Bring a clear photo in natural light and explain what you want to leave behind as well as what you want to wear next. The artist may suggest a larger scale, a different placement or a subject with enough contrast to disguise the old work. Cover-ups usually need more planning than a fresh tattoo.
Laser fading and the hybrid approach
Sometimes a few laser sessions can reduce the density of an old tattoo without removing it completely. That gives the new design more options and can keep it from becoming unnecessarily heavy. The right route depends on the skin, pigment and time you have available, so discuss it with both a qualified laser provider and your tattoo artist.
Do not hide the old tattoo in your enquiry. The more accurately the artist sees it, the more useful the first answer will be.