Every year I tweak my lasagna recipe. A few things that never change: if using meat, I make sure it's turkey because it's lighter and absorbs flavor better than beef. I also like adding a veggie - vegetable lasagna is great, but even in my meat lasagna I add spinach. Cheeses: pecorino is great to finish off the cooking process, fresh grated mozzarella is better than pre-shredded moz (this gets really dry between shipping from the factory to the grocery store). Ricotta cheese is not a staple - I think you can definitely get away with just fresh mozzarella and maybe a bechemel sauce.
This recipe combines some of my favorite methods and ingredients.
2) In a frying pan, sautee 1 onion that you've cut up really small along with 4 cloves of chopped garlic (use olive oil for this, it adds a great flavor). Add one pound of ground turkey and continue cooking until the onions are dark golden and the turkey is almost cooked through. Add this to the sauce and cook down for about 20 minutes.
3) Mix 1 medium sized container of ricotta cheese with 3 cups of cooked down, sauteed spinach. Season this mixture as well with salt and pepper.
4) Make the bechemel by melting 2-3 Tbs of butter in a saucepan. Add 3 Tbs flour and whisk together until they come together. Add 2 cups of milk and continue cooking until the mixture has thickened (medium high heat for about 10 minutes should do it). Add salt and pepper to taste - throw in a few red pepper flakes for good measure, too :)
5) To assemble, spray a 13x9 inch Pyrex with Pan or butter lightly, then add 2 ladles of the sauce, enough to coat the bottom. Put one layer of any non-cook lasagna layers over this, then another couple ladles of the meat sauce. You need to put the meat mixture above and below the first layer of lasagna so it has enough moisture to cook thoroughly. Over the meat mixture, add about 3/4 cup of the bechemel and another layer of pasta. Cover this with the ricotta cheese mixture, more pasta, meat sauce, a final layer of pasta, and the rest of the meat sauce. Over the top, pour the rest of the bechemel sauce and enough mozzarella cheese to cover the top. Cover the top with aluminum foil and cook for 35 minutes at 375 degrees. Take the aluminum off, raise the temperature to 400 degrees and let the cheese brown - another 10 minutes.
The key here is to season as you go - by assuring each layer tastes right, you eliminate the need to alter proportions at the end.