Assuming that majority of your work will be related to industrial establishments.

Factories Act: Registration, Safety measures, Notices, Registers and returns.POSH Act: Constitution of Internal Committee, procedure

Industrial Disputes Act: Procedural aspects, Section 2A, 2(k), 10, 31-33

Employees Compensation Act and Employees State Insurance Act.

Payment of Wages Act, Minimum Wages Act, PF/Gratuity, Contract Labour Act.