How to get rid of all the data from cell phone before selling android phone?

You can't completely escape from recovering your deleted mobile contents. Best way to sell to some one who you know and who doesn't know or bother about having recovery softwares.

Don't sell it on shops.

factory reset then use an app like secure eraser to overwrite the data that is still recoverable.

You reset it.

idk that it totally erases everything (i dont trust phones) but as far as common people goes it does..

Reset on settings?

yank out mem chip , just guessing , never had a cell phone yet

Factory reset