Get technical expertise
In this field, you need specialised know-how. So you either need to have a background in medicine or need to work closely with someone who does.
Find a niche
You need to find an area of testing that is in demand or is poised to take off. You might get clues by reading medical journals and keeping tabs on social trends.
Get the funds
If you want to set up a small lab, you could with equipment worth just a couple of lakh rupees. This is because most tests can be conducted with small machines, if you are willing to accept a small batch size. It's the real estate that will cost you a lot.
The National Accreditation Board for Testing and Calibration Laboratories and the US-based College of American Pathologists are the two main bodies that certify laboratories in India. The organisations send across their teams to inspect various facilities. The process should not take more than a couple of weeks.
Most labs hire people referred to them or through job portals. But like in many fields, there is a great demand for good people in this field as well, so people will remain with you only you empower them.
Promise and deliver
This may sound obvious, but many people mess up here. Be clear about what your brand conveys and then back this up on the ground.
Sort out logistics
Decide how you are going to collect samples. Some large laboratories have tie-ups with courier companies. Some have their own people.