The first step is to get yourself into a Law Officers chamber or that of a political senior. Unless you are a son or daughter of an MP or MLA in which case you can get onto a State or Central Panel.
There are 2 shining examples:
Arijit Prasad who is now a Senior in the Supreme Court has spent his entire career from 2001 on the Central Govt panel. He did Income Tax cases exclusively and it gave him a lot of visibility. This happened because his father was a Congress MP from Assam, but he built up relations on his own which ensured he continued under the BJP.
Zohaib Husain also has spent 15 years on the Government panel after joining Mohan Parasaran when he was SG. He continued into the BJP regime and has been a briefing counsel in many cases before being made ED and Tax standing counsel for Central Govt before the Delhi High Court.
Both of them have made the choice not to have private practise (very few private briefs come the way of someone who has spent all their time on Govt panels). Now the trajectory would be towards judgeship, ASG, etc.
Remember however that if you choose this path, there isn't much money in it (unless you choose less scrupulous avenues).

empanelment in itself is not SO difficult - you meet a few seniors, you make a few requests to the right people, your name gets put in. empanelment happens en masse, or notifications are issued even for few (at times, one single advocate) at a time. bt the actual marking of matters after being empanelled - that's the real game and that's where the mighty and the influential take the cream of the work

Shreeyansh Lalit is only four year into practice and has already been appointed as a senior lawyer representing the U. P. government in the Supreme Court. How can a first generation advocate get fast tracked like this? How much time does it take to get empanelled to various government departments?