We planted oodles of onion sets this year. I also have onion seed, which I will direct sow because I can't seem to keep seedlings alive long enough to plant them outdoors - probably because I start them way too early. The seeds should form bulbs by fall, which can be left to overwinter. That's the theory, anyway - this is my first time trying it. Here are some of our onion sets:
We've planted them close together here, right next to the sides of the bed so we can harvest them early for green onions. We also planted a bunch several inches apart so they can get big. Yum.