How to choose the best:
Banana

Touch

I don't think this one really needs spelling out, but here it is anyways:

Firm = unripe
Medium = ripe
Soft = overripe

See

I don't think this one really needs spelling out, but here it is anyways:

Green = unripe
Yellow = ripe
Brown = overripe

Smell

Give a good sniff: overripe bananas have a distinctive aroma — you know the one.

Some more details:

How to clean

Do yourself a favor and give them a quick rinse in water with just a dash when of vinegar when you bring them home, to help avoid fruit flies later. Just make sure to try them off well after!

How to store

Store at room temperature, and hanging is best to help avoid excess bruising.

Some fruits, such as apples and pears, release ethylene gas as they ripen, which in turns speeds up the process on bananas — so if you want to get your bananas ripe faster just leave your bananas enclosed somewhere (like a paper bag) with an apple overnight.

When it's in season

Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec.