Oh my gosh - now I totally want lasagna now!!!!
And yes, adding egg to the ricotta is a super idea - I also add some shredded parmesan cheese (not the kind in the green bottle - I mean, REAL parmesan) and a little parsley.
And cooking with the foil off is a surefire way to keep things from getting too runny.
I do use the liquid from the tomato can though (unsalted) so it balances it out since I'm not cooking it covered (I love a good crunchy crust too).
I used to have this problem too. Two things that helped, other than making certain your ingredients are thoroughly drained of any moisture: Bake covered for 30 minutes or so, then bake uncovered for 15 minutes. Once the lasagna is hot and bubbly all the way through, take it out of the oven and let it sit on the counter top for about 10 minutes to "set". This helps a lot.
I always have a ton of lasagna left over since there are just two of us most of the time now. I've found that the next day or two, it's much easier to cut, doesn't weep at all, and tastes better. So if all else fails, you can make it ahead and reheat.
I use a thick sauce usually Prego, because 1. It's basically the thickest store bought and 2. They have so many choices now for different flavors, and you can mix it up. I put both Parmesan & Romano cheeses in my Ricotta along with pepper and at least 2 eggs, depending on how big or how many lasagnas I am making at the time. I have a large family with 6 children, ALL boys! My parents and brother always request a small pan when they hear I'm making it. I've tried both oven ready, and regular lasagna noodles. There doesn't seem to be a big difference as long as you drain the regular noodles really well. As well as making sure I drain the hamburger and Italian sausage I use. However, taste and texture wise my family prefers the regular noodles. I use the oven ready noodles if I don't have tons of time. Also, some in my family like pepperoni in their lasagna. Obviously, pepperoni is very greasy, and can make it appear watery. I try not to use much, just enough to make them happyand I use a smaller separate pan for the lasagna with pepperoni. Oh, I have also added cottage cheese a few times to the Ricotta. I make sure it is drained really well. Almost to the point that it is dry. I never bake the lasagna covered! Ever. I add my last layer of cheese to the top 20 mins or so before lasagna is done, and usually let stand 15-20 mins. Hope any of these things help you, most if not all were probably already mentioned by others. Good Luck! Happy Eating!
I usually drain my ricotta to remove about 1/2 the moisture and then add 1-2 eggs depending on the size of the lasagna. Personally, I'm not a big fan of the oven-bake pasta. I use either boxed or fresh lasagna sheets.
I add eggs to the ricotta, make my own sauce so it is very thick, and I bake it completely uncovered. As long as the last layer on top is sauce, cooking it uncovered is fine; it allows more moisture to cook off and the noodles won't dry out. When I take it out of the oven to rest before cutting, I put a layer of cheese on top. The heated lasagna melts the cheese, and resting allows any leftover moisture to be absorbed into the lasagna instead of draining to the bottom if it is cut immediately.