When a girl is on her period and you finger her. The cotton represents the tampon.

To have amazing or wild sex with another person.

This phrase stems from cotton fields that were tended by slaves.

Pick my cotton in other words means 'do me a favor' but is not a question, it has more of a 'do it' tone.

Usually the favor being asked is a simple physical favor such as turning off a light or plugging in cables.

Alternatively it can be used as 'I'll pick your cotton' which is used to say, 'Yes I will do you a favor, but I hate you.'

The act of to pulling your underpants out of your ass crack or fixing yourself after being the recipient of a wedgie.

picking up white girls (if you're a black guy)

When a black guy fucks a girl with a tampon in.

the act of doing an excess of tasks in order to do something else.