When buying your seed stick to one type (super sweet, summer sweet etc) as mixing causes misses in the kernels.
Sow the seed in modules 6 weeks before planting out and plant out after your last frost date (for caution you might want to add a couple of weeks onto the frost date, cold kills sweetcorn).
Plant in blocks, we do ours at about 18in grid spacing, some gardeners go down to a foot. (Bigger spacing allows ease of access for picking, not sure also if close spacing encourages smaller cobs, just my observations).
As a guide we grow 40 super sweet plants for two of us (usually Swift), we don't freeze any and always end up giving some away.