How To Get Your Desired Job After Interview

how can somebody go to interview and have the assurance that he or she will get the job?because i have my sister who have took some interview on unity bank and other banks but no avial.but she have hope to the lenght of going to the market to buy suit materials,all the way from calabar to Aba when she was coming back from the interview at ABJ.
u see u can do the same if due it fall u or ur friends mook at you but take heart.
thank you