For the best possible taste you should pick fruit when it is a solid color (red, yellow, etc.) from top to bottom, but still firm.
Also remember to pick often. You may need to harvest daily or every other day to make sure that you can get the tomatoes when they are perfectly ripe. Keep an eye on how the fruit is developing.
Also remember that the cold can degrade tomato flavor, so store tomatoes on your kitchen counter, where the temperatures are above 50° F (10° C), instead of in your refrigerator.
The best-tasting tomatoes have a balanced ratio of sugar to acid, and the sugars increase as the fruit colors. Tomatoes that ripen during the longer days of summer have more sugar than those that mature during the shorter days of late summer, and therefore can taste better.
Tomato ripening tricks
If when the fall months come there are still several green or partially ripe tomatoes on your vines, but not enough warmth and sun to mature them properly, don’t give up on them! There are two ways to ripen green tomatoes properly.
Tomatoes ripen from the bottom to the top and from the inside out. So never put them on a windowsill. That will only turn them red, not ripe. What you want to do is put them in a warm, dark spot and cover them with a single sheet of newspaper. These conditions are the ones tomatoes need most to continue their ripening process, which is internal. Light at this point is not necessary any longer.