Question about when plants reveal gender and cloning

I've looked, but haven't really found a good answer to this question.

When do plants start to reveal their gender? That is, when the female plants start showing their pistils and the males start showing those little balls near the stem.

The cloning question: When should I take clones from my plants? While they are vegetative? Also, how tall should the clones be?

Thanks,
Australia

plants usually pre-sex around 30 days from seed assuming their healthy... I clone lower branches during vegative growth clones a few inches with several leaves