Company Secretaryship

CS is a course which can be done only be getting yourself registered with the Institute of Company secretaries of India.
There's no college for doing the course.
The work of a CS includes looking after all the legal compliance which are required to be done by a company. The laws in which a CS excels includes corporate laws including company law, labor laws, FEMA and RBI compliance among others. Also, CS is considered as a key management personnel for any company and therefore, has more responsibility than any other normal professional.
It pays off nicely, too.
The initial package on an average for a fresher CS ranges from anything between 25k to 40k.
Depending on your skills, knowledge and temperament and experience you get it enhanced.
Just for your reference, have a look at the link below, might give you an insight into the remuneration part.
http://canotes.in/list-10-highly-paid-company-secretaries-india/
All the best.

The primary goal post-qualification should be to gain as much experience as possible. Thereafter, courses can be pursued part-time or in an executive format.
Courses depend on where your interests lie and what you have already done. If you have done B.Com, it is advisable to pursue LLB. If you have already done an LLB, you can pursue the various courses offered by NISM Certifications, or BSE/NSE certifications.
Alternatively, you can go on a tangent and pursue LLM/MBA with some kind of corporate/financial specialization.
You always have the option to take advantage of the MoUs of ICSI and acquire memberships in CISI as well as ICSA.
I can suggest pursuing CA/CWA but won't recommend it as one can practice/be employed under both qualifications and hence if you work under one, the other is useless (it does look fancy on your CV but that's about all it can do).