I need an Determined advice from expertise

I'm an B.Tech graduated student and present condition of IT seems to be bad and my other alternate is to prepare for govt. jobs and at present am having an option of Postal assistant/sorting job regarding Andhra Pradesh state. so kindly give me an detailed advice on preparation for it and to your notice, am OC candidate.
I've seen that max marks for it was 100 and in my district (OC)we are having 6 seats ,so what could be the good marks to be scored to get it and as you are seeing in the past what's the best marks scored by candidates for an max of 100.
And please do give me an eminent message for preparing it and get succeed in it.