DRDO has Recruitment and Assessment Centre (RAC) for Scientists (Group 'A' Class I Gazetted Post) recruitment and CEPTAM for recruitment of DRTC, Admin & Allied Cadre (Group ‘B’ and Group ‘C’) recruitment
Each individual lab publishes the requirements of manpower in what’s new section of DRDO website and in its lab page what’s new section as and when required.
Apart from inducting Scientists 'B' (Entry Level), DRDO has following schemes for inducting Scientists 'C' and above (upto Scientist 'G') based on number of years of experience:
Lateral Recruitment for Scientist 'C' and above as per requirement of the Labs.(Through Advertisement)
Talent Search Scheme (NRIs) for Scientist 'C' and above subject to suitability in DRDO Labs.
You can apply for summer training to Director of a suitable lab as per your discipline. You may visit DRDO website https://drdo.gov.in for this purpose.
No experience required for the post of Scientist B (entry level). And for other Scientist post, there is experience needed respectively as per guidelines. Goto website https://rac.gov.in