DON'T ever pay a deposit or send any money before you see the item. Scammers often ask for a "booking fee" via Airtel Money or Mpamba to "reserve" an item for you. This is a classic scam.
DON'T rely on stories about the item being at a border post (e.g., Mwanza) needing a "clearing fee." See the item with your own eyes first.
DON'T give out unnecessary personal information like your bank account details, home address (unless necessary for viewing), or copies of your ID.
DON'T transact with sellers who refuse to meet in person or only want to communicate via WhatsApp text. A serious seller will be willing to speak on the phone and meet.
DON'T accept seller claims at face value. Do your own verification.