When picking a lime, make sure you look for one that is firm and heavy for its size. The skin should be smooth, thin, bright green with no wrinkles or spots. If the lime gives a little bit when you press your finger in it, then it is ripe. If it’s too hard, leave it for a few days until it softens up. As limes are typically on the smaller side, the heaviness of it in your hand can often determine if the fruit is ripe. Additionally, limes should have a sweet smell to them; if the aroma is off or odorless, then passion it.