There are a lot of little courtesies in golf, from the obvious (such as not talking while someone is taking their shot) to the obscure (not only avoiding stepping on a player’s putting line, but also on their through-line—where ball might roll if it glides past the hole). Tending the flag lies somewhere in-between.
For the most part, flag tending is a part of the putting rituals. Once everyone is on the green, it is customary for the person pulling the flag to ask if everyone can see the hole. On occasion, due to distance, shadows, undulating greens or just plain poor eyesight, a player will request that the flag stay in. At this point, tending is necessary because hitting the flagstick while putting constitutes a one-stroke penalty.
Typically, the person closest to the flag does the honors. I also try to make it a point to do the flag tending duties in rotation with the other players. And if I’m playing with older gentlemen who might have trouble bending over to pick up the flag afterwards, I just try to take over the job for the round.
When tending a flag, the thing to do is to grasp the pole at arm’s length and pull it straight up slightly out of the bottom of the cup. Stand still until the putting player makes contact and the ball begins its forward motion. Then, lift the flag straight up out of the cup and quickly step away from the hole. Place the flag on the edge of the green.
A tip: To avoid leaving your wedge or chipping iron behind, rest it on top of the flag. When you replace the flag, you’ll remember to get your club back.
I recommend pulling the flag out slightly before the putt to avoid the embarrassment of being unable to remove a stuck flag before the ball arrives. Also, make sure that you pull it straight up to avoid the embarrassment of pulling the cup out of the hole.
Players just off the green occasionally will request that their partner or fellow competitors tend the flag for their chip. I’m not sure this is a good idea, however. There is some convincing statistical evidence that players make more shots from off the green with the flagstick in. I suspect it’s something to do with the flag acting as a bit of a backstop.
A final reason for tending a flagstick—rarely used in my experience—is to lift the flag above the hole so that a player taking a shot can see the hole’s location from a blind spot.
When replacing the flag, put it straight back in and before leaving, ensure that it is standing straight up and is secure. A flag that leans against the side of the hole can cause damage. People who cause damage to the greens accumulate bad Golf Karma.
There are some hazards to flag tending in golf. First is that a player must request, or give permission for a fellow player to tend the flag. Unauthorized flag-tending is a two stroke penalty if the tending might have influenced the movement of the ball. Second, if the player’s ball strikes either the flag tender or the stick, it’s a two stroke penalty.
When on the green, player should take care not to stray near the flag. Under the rules of golf, anyone standing near the flagstick while a stoke is being made is deemed to be tending the flag. That’s ok in a friendly round, but in competition, someone might try to take advantage of your proximity. If you are close enough to be considered a flag tender, but don’t have permission to do so, you could get hit with a penalty.
The details of flag tending in golf are found in Rule 17.