Beetroot
Sow thinly in rows 30cm apart. Cover.
Sowing
Both Monty Don and Alys Fowler start their beets off in modules, and plant out later.
Sow 2 seeds per modules. You can thin them out (eating the small leaves), or follow Monty's advice, and leave the beets to grow in a clump, forming smaller, but more numerous (and tasty?) beets.
For early sowing outdoors, you should warm the soil with cloches etc.
Cooking
There are beautiful ringed varieties, however, these loose their colour easily, so IMHO, aren't as good when pickling.