Study well these texts regarding shinä: the Lamrim Chenmo and Liberation in the Palm of Your Hand, and also Geshe Lamrimpa's book [How to Practice Shamatha Meditation].

Also, you need good conditions to have success in shinä, so don’t plan to do this right away. First, you need to purify and collect merit and then you need to study, to have as much knowledge as possible.

When you have more experience in lamrim, then do shinä retreat, based on Highest Yoga Tantra. If you can do it this way, then it can be very rich, like ice-cream with sugar, cream and many things. This makes your retreat very delicious, yum, yum. So, then your three-year retreat is very productive, it doesn’t become an obstacle, or a cause of lung. If one doesn’t have a lot of merit, then one becomes sick or obstacles can occur.