Here I listed some basic things while buying a phone 1.Press all the buttons to ensure they are responding well and showing the corresponding letter, figure, punctuation or character when pressed. 2.Have someone call you to confirm that the phone rings and vibrates properly. 3.If the phone comes with earphones, plug it in, play music, ringtones, radio and make calls to be sure it is working. 4.Generally, browse through the phone menu.