Do you prefer to be told flat out?
Would you rather be taken aside somewhere private?
Be told flat out but in private. It's embarrasing but better to have one person find out than many find out later.
Do you prefer a physical communication , you know like someone keeps wiping the side of their mouth while looking at you.?
No, because I might not take the hint.
Would you prefer not to be told at all , and figure it our for yourself.
No, because I might not notice right away if at all. If I end up noticing it later, it would be even more embarrasing than being pulled aside because more people would have seen my faux pas.
How are you more likely to go about telling someone else?
Try to pull the person aside and whisper to them about the booger hanging, fly down, toilet paper stuck to the back of the shoe, etc. Tell them not to worry about it if they seem really embarrased because it happens to all of us from time to time.