What jc121 said!
One thing which might help a newer shooter in establishing npa is to pick a "pivot point" for each position and once your npa is established, do not move that pivot point until the string is completed.
I have tried coaching several new shooters who cannot maintain a position for 10 to 20 minutes required to complete a string. Until a shooter is able to maintain npa throughout an entire string, they will not shoot consistent, good scores!
Being a right handed shooter, my left foot is my pivot point for offhand. To shift npa to the right, I move my right foot to the left (all movements are given in relation to a line from target to rifle muzzle), to move npa left, move right foot to the right. To raise the muzzle of the rifle with my normal amount of retained air, I move right foot to the rear and vice-versa.
I shoot the crossed ankle sitting position, which I know is frowned on by most shooters, but what with arthritis causing extremely stiff back and some dunlop disease, can no longer attain a crossed leg position. Crossed ankle position works for me and I simply move heels left or right for windage adjustments to npa and pull ankles closer to body to raise muzzle.
Prone, the left elbo is the pivot point. To swing left or right swing entire body L or R and to raise muzzle, slide to the rear without moving left elbo.
All of this seems quite basic to all you old timers out there, but hopefully will be of some help to at least one newcomer to our ranks.
Practice your npa while dryfiring (another excellent tool in improving one's scores) and pay attention to the feedback which is so obvious when not masked by recoil of live fire practice.
Regards,
hps