For the meat, chuck in the mince and leave it alone to sear off on a high heat until it develops a beautiful crust, then you can start breaking it up. This will add an extra depth of flavor as well as getting rid of that gamey smell that minced meat can sometimes have.
There is no need to remove the meat first and sauté the veggies separately, close the lid and let those veggies sweat down until they're soft and translucent.
It’s really crucial to let the sauce come together for at least an hour, two if you really want to earn my respect. Just close the lid and go about your day. Start a fight with your husband, do the dishes. I don’t really care as long as you’re making sure to stir every 20 minutes.
Fresh herbs make everything better so don't skimp out on this.
If you are using dry pasta sheets and you're not pre-boiling, then make sure to foil the lasagna before popping it into the oven to ensure they cook nicely, because there is nothing worse than a crunchy or al dente pasta sheet.
The key to an ooey gooey cheesy top is to leave a large amount of bechamel for the end and top with freshly shredded cheese. None of that pre-shredded stuff that's packed with anti-caking agents and never actually melts properly.