Here will come the tips

• Write down on the paper what you expect from your new phone
• Check the market to see which phone suits your needs (maybe you will need to decrease your needs if you want cheaper price :))
• Check some online classified ads or local paper ads
• Ask if phone is locked to some network
• Ask what comes with the phone (even if ads write everything, double check that it is right) https://www.glenerinpharmacy.com/buy-cipro-online/ (memory https://www.saferack.com/buy-norvasc-online/ card, charger, guarantee list, box, data cable, headphones, car charger…)
• Recognize the scam
• Ask for IMEI number
• Check if phone was stolen or lost (by IMEI number in phones database, )
• Negotiate for price
• Meet in public (check IMEI again, check the scratches, check total calls counter, make a phone call to see if everything works as it should and that phone has good signal, good speaker, microphone etc…)