g'day
now we all now the way to get the best results is to combine the physical with the spiritual, so here's some free advice:
first cross the legs while sitting on the floor, set the clock in the mind, keep breathing while you feel comfortable, what i learned the breathing process interact with the life force around the universe - spiritual it's not just a oxygen with nitrogen gas
if the breathing goes well, at some point the air becomes liquid you will feel you gonna drink soft liquid through your nostril, it goes down to the abdominal and sitting in the middle, i learned there are three collectors where the life force can be accumulated
do you have a mentor that guides you?
you should have
there should be no abdominal muscle pain suppose you do alright each session, your body get relaxed, mind become clear, the breath length will be extended by your consciousness try to extend 2 sec when you feel comfortable your current breath length