I have come across students finding it difficult to learn the surface area formulas of cube, cuboid, cylinder, cone, sphere, etc. You can pick up a real life object like a tennis ball for a sphere, or an ice cream cone for a cone and so on. You can also check on the internet and search for easy method to remmeber a formula. I have come across many websites which explain the formulas easily depending on the area. As mentioned in another answer, you can use catch phrases or relate to a song or any memory for the formula.