Some find that the Valsalva technique works for them. Avoiding sleeping on one's left side also helps.

Some attempt to restore Vagus nerve tonality using various techniques, of which the Valsalva is one. Others including plucking the tragus on the ear (the small cartilaginous lump above the earlobe) repeatedly.

Magnesium supplements may help. Start with 100 mg per day, and try rising to 400 mg. Note that I am NOT a nutritionist, nor am I a physician/expert. I'm just relating what others report having worked for them, and often merely adding magnesium (malate, taurate, citrate variety, take yer pick...) helps. Your kidneys, if healthy (this is important!!) will typically eliminate what your body doesn't need, so you shouldn't worry about 'overdosing', although going crazy with magnesium would be a problem ere long. Ask your doctor for his/her agreement before embarking on such a regimen.

I found that my worst episodes of AF happened when I was carrying too much visceral fat...internal and around the organs, not the 'spare tire' kind. The problem is the strain on one's innards, as well as the accompanying rise in blood pressure, when bending over and when lifting heavier items. That will trigger AF...in me and in some others.