Lasagna is my "friends coming for dinner" dish. I rarely make anything else as people always request lasagna and i can actually cook other things.
My tips.
Long slow simmer on the ragu. I normally start it cooking after lunch and then keep it simmering away slowly until assembly time which is late afternoon/early evening.
Meat-wise I use either beef, beef/ pork, or lamb depending on the combination of guests as I have both hindu and muslim friends. Unless the non drinking muslim is coming I always add red wine (even for kids).
I make my own béchamel / white sauce using an old delia recipe that contains cream (so possibly not very traditional!) I always add nutmeg.
Assembly is meat, pasta, white sauce, meat, pasta, white sauce, meat, pasta, white sauce. Cheese. The top white sauce layer should be thick and totally cover the pasta underneath.
I tend to use whatever cheese is lurking in the fridge on top - so cheddar always and sometimes parmesan, mozzarella or brie remnants.
Long slow oven cook. It tends to have visible sauce on day 1 (which I like) but by Day 2 it will hold it's shape when you lift it out of the dish.