I spent a very enjoyable afternoon doing a cooking course with a lovely Italian Nonna in Tuscany whilst on holiday there. She spoke not a word of English, but luckily her lovely sons were there to translate...
We used a 50/50 mix of pork and beef, plenty of finely chopped veg (carrots, celery, onion), a decent glug of wine and not as many tomatoes as you'd think. She was very clear that we were not to boil the meat.
I've followed her method ever since, except I do use tinned tomatoes and probably make it a bit wetter than she'd approve of.
Totally agree with all the people saying not too much meat per layer (I put 4 layers in a standard depth lasagne dish), and fresh pasta makes such a big difference. I think there's a sound logic to this, as fresh pasta is pliable, so when you layer it up it naturally comes into contact with the sauce, so it cooks in a very different way to dried pasta, which has lots of air pockets around it (unless you have thick layers of wet sauce in which case it will absorb moisture from the off). I always make my own pasta for lasagne (5 mins to mix, 5 mins to roll out) too, but I'd definitely get fresh pasta if I didn't do that.
Also agree about letting it stand before you serve it.
I make double quantities of the sauce (one pack of beef mince, one of pork) and freeze half. Takes most of the faff out for the second time around.
Done well, it is the food of the Gods. Done half heartedly, it can be a disappointing chore.