A short list, because a marketplace only works when strangers can trust each other.
Photograph the actual item you are selling, not one from the internet.
Say what is wrong with it. A scratch you mention is a detail; a scratch the buyer finds is a wasted trip and a bad name.
Put the real price in the price field. A number designed to get people to open the listing is not a price.
Anything illegal in Tanzania, and anything stolen.
Drugs, weapons and ammunition.
Counterfeit goods and pirated media.
Prescription medicines, supplements making medical claims, and anything sold as a cure.
Live animals, human remains, and protected wildlife or ivory.
Sexual services and adult content.
Other people's personal data, accounts, or identity documents.
Money, financial instruments, and anything that is really an investment offer.
Haggling is normal and expected. Insults, threats and harassment are not.
Do not pretend to be someone else, and do not post someone's private details — their number, their address, their photograph — without their agreement.
If you are not going to turn up, say so. Wasting a stranger's afternoon is the fastest way to make a marketplace useless.
A listing may be removed and an account may be suspended, without warning where the breach is serious.
We act on reports and on what we can see. We are not able to referee what happened between two people after they left the app, and we do not decide who is right about a sale that already took place.