Corn is ripe when the silks look brown or black and dry. Different varieties take different times to mature but I think around 6 weeks to 2 months. I have quit growing corn because the squirrels wont wait till it's fully ripe.

When the coon or fox show up and eat it, really, of course it is too late by then.

Walk through your patch and pay attention to the silks on all the ears trying to remember which ones were the darkest and driest. Go back to a couple of those ears and pull back the husk to about half way or just remove the whole ears and shuck them. If the kernels are filled in so much that there is no open space between them it is ripe enough to pick or beyond. The kernels just keep getting fuller beyond that stage and sugar content will start to diminish especially in the Su and Se types. Most of all, take a bite, if it isn't very sweet you either waited too long (go back and sample some ears with lighter silks) or you planted a variety that didn't suit your site this year. I had my first wrong variety in over 10 years this year, wasn't very sweet and didn't taste very corny.

Michael

I am new too. I planted an eary type that gets 3-4 feet tall. Most of ours is done now (eaten). I had the same question.
I read that corn is ready 16-20 days after the silks appear. You stick your finger nail in a corn kernal and milk comes out and the corn has to be all the way to the end of the ear. I just checked tha same fatest ear I could find every few days. I suppose it depends on the variety, zone and weather. We had a cooler summer. Sure was tasty to just go out and pick it to eat...FUN! Next year I want to plant the tall kind with more ears.