If you are like me you have a hard time telling when a tomatoes is ripe enough or too ripe. Since the ultimate test of ripeness is in the taste a good place to buy tomatoes is at the local farmers market. Most of these sellers will have samples of their tomatoes. If  you are growing tomatoes it is hard to tell when to pick them. According to Go Tomato Gardening you want to bring them indoors when they are pink around the top. Or when they are green, full size and begining to split. You also want to leave part of the vine attached to them. I have a hard time letting the green ones last until they are ripe as I love fried green tomatoes.