One legend has it that maple syrup was discovered when an Indian put a tomahawk into a tree directly above his wife's cooking pot. The sap flowed down the handle into the pot sweetening their meal. Another legend has it that the Indians observed squirrels chewing the bark and licking the sap from the maple trees. I live out in the country with multiple maple trees and squirrels and I have never observed this behavior. In any case, maple syrup is strictly a new world product and has to be imported to Europe.
Tapping maple trees is done in the early spring, when the days are warm and the nights are cold. This is when the sap is flowing best in the tree. The rule of thumb is one tap for every foot of the tree's diameter up to four. Tapping a tree does not hurt it. There's a maple farm in Vermont with a tree that has been tapped every year since the Revolutionary War. Drill a hole about 4' off the ground, about 2 inches deep and the exact width of the spile that you insert into the hole. The hole should be angled slightly upward to allow the sap to flow down into the bucket. Originally, spiles were hollow sumac shoots. I use an old-fashioned metal spile and bucket collector. Professional maple farmers use plastic spiles and tubing to gather the sap directly into tanks. You can purchase spiles and tubing (or buckets) at most farm supply stores.
I drilled one hole in a maple tree with a 3' diameter. I wanted to start small to see how much work was involved before I went into small scale production. Every morning for a month, I replaced the full bucket with an empty bucket and brought the full bucket into house and poured it into the cookpot on the back burner. If we were home and awake, the cookpot was on a low simmer to evaporate the maple sap and condense it down to syrup. If we had wall paper in the kitchen, it would have peeled away from the humidity. Our gas bill took a noticable bump that month. It takes 40 gallons of sap to make 1 gallon of syrup.
If you were going to sell it, then you have to make sure that it's thick enough (67% sugar content) and grade it according to color. Since I was only making it for my own personal use and to give it away, I considered it done when it looked and tasted right. I got about 2 gallons of syrup from that one tap and decided that I didn't want to go into small scale production. I'll make maple syrup for my own use every other year or so. You can store maple syrup indefinitely by freezing it.