As a team leader, you have to look after the performance of every employee. You should help your subordinates in working hard and improve as well. You may get to handle a weak candidate, who might face a lot of hurdles in his work. Make sure that you clear his queries and assist him. Try to give him enough exposure. Make him interact with different employees. S/he should familiarize herself or himself with the handling of customers. Train him/her well and give him/her the confidence to do the work well.