I've seeded 100 acres or so per year for he last 20 years with a JD 750.
*In spring, set the drill in the shallowest position.(750 deere) If summer seeding, like after wheat, go one hole deeper.
*Try to avoid seeding into very dense corn stubble. The seed will germinate, but the stalks shade the ground, and the plants will grow more slowly. I usually seed the spring after corn silage harvest, and if the ground is steep, plant a cover crop after silage until the following spring.
*Start with a clean field. You will not need roundup ready alfalfa, but should definitely consider a round-up burndown prior to planting, even if seeding early.
I have never lost a stand no-tilling alfalfa. It is fast, easy, and low cost. your fields will be smoother, so less dirt in the hay, too.
In my neighborhood, there were stands that were lost to the drought... and all were tilled fields. My agonomist was amazed at our stands. Minimal weeds, healthy plants. The only difference was we did not seed new weeds with tillage in spring, and conserved moisture by not working the soil.