What's the customary technique for adjusting the magnetic compass

[dov_elyada]

My magnetic compass was way off. I found the screw that adjusts it. I took the compass off and adjusted it away from the aircraft and from interfering steel structures and objects. This I did using lines-of-sight to geographic references for which I knew the bearings. But how can I be sure that the adjustment remains valid once I put the compass back in place?

I realize that I may have been "re-inventing the wheel." So how experienced pilots do it?

Thanks for your advice
Dov