What do you mean exactly by The only way to free yourself from the cycle of birth and death is to engage in devotional service to the supreme
I'm guessing it doesn't mean just to do good and pray.
Quoting: Anonymous Coward 12046133 Praying is devotional service.
According to the Vedas, there are 9 kinds of devotional service. You can do any 1 or all 9 of the devotional activities and achieve perfection.
1) Hearing about the Lord, his name, his past times, his characteristics.
2) Chanting about the Lord, his name, his past times, his characteristics.
3) Remembering the Lord, his name, his past times, his characteristics.
4) Serving the Lord, his servants, his servants servants.
5) Worshiping the Lord, and anything related to him.
6) Offering prayers to the Lord.
7) Executing the orders of the Lord.
8) Becoming the Friend of the Lord, for he is your greatest friend.
9) Completely surrendering to the Lord, all your possessions as well as your body should be used to please the Lord.
Those are the 9 types of devotional service and if you apply them to your current religious beliefs, you can be assured of your perfection.