what should a structural engineer aim at ....?

It depends on what one wants to do at work.
Structural Engineering covers a large territory, not just buildings.
Airport design, Chemical/Polymer manufacturing facility design (for support of plant and machinery), Bridges and elevated transport ways, Design for marine or other corrosive environment and so on.
In the West 3D printing is assuming importance for some applications.
In addition to a sound background in structural design it is important to acquire some skills with appropriate higher end CAD software.

i want to go in building construction/ detailing , so what should be practiced to become good in detailing

This is not my area. It interests me though. Here is a 400+ page thesis from Sweden which may give some information:
https://publications.lib.chalmers.se/records/fulltext/188834/188834.pdf

if your intrest is in structure you will definetly earn money and fame.
1.if u r doing masters Frm IIT den take experience of few years and open your own consulting firm.
2.if u r doing M.S then you will get defineltly good job.
Bt see your strength and weakness
n see whether you will be good employee or business.
regards Bitochen.