firstly,there is an old saying :opportunities are always left for someone who has made a good preparation.so no matter what happens ,we should always exercise ourselves before it's too late.
Secondly ,try your best to know more about the job you want to got.
because if you know more ,you will gain boss's believe and the boss will think you are more interested in the job than others.
thirdly,have a good appearance.keeping smile and confident is also very important ,because good performance will give every boss a good impression.