Give a donation to “St. Anthony’s Bread”.
If your local parish does not have a “St. Anthony’s Bread” fund, then make the donation to your parish church’s poor box. Personally that is what I do.
And to show my confidence (St. Anthony really does help find things), I promise to cheerfully give $5 to the poor box while I’m praying – payable as soon as practical after finding the lost item. I think St. Anthony has extra motivation when he knows there will be a donation to the poor attached to his helping find something. Probably he can see who the $5 will help and how badly they need the help. I know I cannot see that.
I really don’t know much. Except that it seems to work out for me quite well. When something is lost and I am concerned enough to pray to St. Anthony, it gets found.
Just remember to be prompt and cheerful in paying up to the poor box (or St. Anthony’s Bread). And thank St. Anthony for his help when you put the money in the box.
If your Catholic Church doesn’t have a poor box, then I feel sorry for you. I know of a few like that around here. Personally I would not feel that I was in a Roman Catholic Church unless there was a poor box and candles to light for Mary. Although I am a recent convert, that is how I remember the Catholic Churches from my childhood in upstate New York. I am very happy that my local parish has poor boxes, some statues, candles, adoration chapel, First Friday devotions, etc. If they didn’t, maybe I wouldn’t have converted. I feel at home in my parish church.