I do hope someone can answer this Huff, because I've been told "harvest just before it's ripe" which sounds tricky.

We used to grow Sweet corn on an allotment and harvested when the silky tassels at the end of the cobs had turned brown. Best to check by peeling back the leaves and pinching a kernel. If the juice is milky then it's ready to twist the cob away from the plant. Hmm, lovely memories of fresh Sweet corn.

I've just picked mine, I waited till the silk tassels went brown, I put them in pictures a little while back, with and without all the greenery on, go and have a look :o)).
Don't add salt when cooking also put them in rapid boiling water for no longer than 10mins or they go tough.
Hope this help's. :o))