Generally speaking, any pumpkin in the grocery store should already be ripe. But if you are picking one yourself, here's what to look for: 1.The color of the pumpkin should be pretty uniform with no large patches that are a different color. 2. The rind of the pumpkin should be hard. If you can poke your fingernail into the rind, it's not ready to harvest yet. Unless you have those really long, pointy fingernails. If you do, let someone else check it... 3. And if you knock on the rind and the pumpkin sounds hollow inside, it's good to go.