dkra got most of them, but there are some variables that you have to
consider.

An over ripe one will give a "pong" also. Pick the melon up in one hand and
slap it with the other. If you can feel the vibration in the hand you are
holding it with, that is a good sign.

The dry and brown tendril is a good sign. Wait until the leaf next to the
tendril is also dead and dry. Problem is that on a very dry and hot year,
they sometimes get dry and brown and the melon is still not ripe.

Some melons are ripe with a white spot on the bottom. Dixie King a light
green colored melon with yellow flesh is one of them. Dark green Sugar
Babies and Black Diamond are ripe when they turn yellow.

Then, after checking my melons and they pass all of these tests, about 1/3
of them still turn out to be a little green.

Good luck. Dwayne