Depends on the leaves/plant you're steeping. Green tea usually needs to steep for longer than black tea, and black tea the longer you steep it the more bitter it becomes, and herb and white tea's usually need between 6 and 12 minutes. It also depends on if you're doing loose leaf or packaged teas.
My mom steeps her green tea for 2 to 10 minutes. I steep my earl grey for 5. She steeps her chamomile for usually a short amount of time, and I steep for at least 7 minutes.
Some teas have instructions on them but most are generic times that are copy-pasted and not specific to the actual tea you have in your hand so be careful of that. If the tea is supposed to be dark, then steep it longer. If it's supposed to be light, like chamomile tea, then you want a shorter time.