Ricotta cheese is perfect for lasagna because it does not melt like other cheeses which is why it is preferred for lasagna. To keep ricotta at its "best" for this recipe, drain the excess water (this will also keep your lasagna from becoming watery) and if you are going to add anything to your ricotta like spinach, mix it together really well before adding it to your lasagna. To drain excess water from the ricotta, place it in a strainer. Cover the ricotta with plastic wrap and place a heavy object, like a small plate, on top of the cheese. Place the strainer and bowl in the refrigerator and let stand 8 hours up to overnight.