Start with solve atleast 10 yrs PGI papers with explanation so that you get a gist of your preparration and information you have before starting the preparation.

Mostly the trick is AIIMS exam questions are asked in PGI with a little modification and twist so solve AIIMS questions as well.

Do not forget to revise important concepts.

Make a schedule and revise things accordingly.

Get good standard books for preparation even if ity is not in bulk.

These few steps can help you in overall good preparartion.

All the best!