Rule #2: Be aware of your surroundings before you ask for a piece of gum.
I think we've all been in that situation where we're dying for a piece of gum, and we reach into our purse (or pocket) and as we pull out some gum, and the person next to you asks "Hey, can I have a piece?". So you look at the four pieces you have left in the pack, and say "Sure!".. And then the three other people standing around you look at you with their puppy dog eyes.. So you feel obligated to ask "Does anyone else want one?" and suddenly, you're throwing away your empty pack in the trash can.
Sharing is caring. I'm all for that. But there's just something about gum.
Because of this, I've decided that if you see someone pull out a pack of gum and they don't offer any, look around before you ask for a piece. Are there other ears around that might think they need gum now, too? Is the gum owner now going to be down more than just two pieces of gum because you asked?
If the gum owner asks "Does anyone want a piece?" first, then it's safe to assume that they've figured out the gum to people ratio, and they know they have enough to share. But if they're asking everyone only after someone else has wiggled their way into their gum consumption, then politely decline - there's a decent chance it's out of obligation.
Special Note 1: Maybe it's just me, but I know that when I use up a pack of gum, I'll forget I've used it up and won't restock. So because I've distributed the last of my gum sticks unexpectedly, I'll be gum-less until I set my Reminders on my iPhone to remind me the next time I'm at Walgreens or Albertson's.
Special Note 2: One way to guarantee that I won't ask you for gum is to bust out some green gum. I don't care what flavor it is, you can keep that green gum all to yourself.
Special Note 3: One of my best friends growing up used to ask for gum every single day. Every day, without fail after band (because you never chew gum during band unless you know that you can chew to time with whatever song you're playing.. And also, it just might mess up your embouchure). It became a tradition of sorts. I also added onto that tradition by giving him a huge pack of gum (like, a box with 16 packs of gum in it) for his birthday and Christmas. He'd still always ask me for gum, but there'd be those random days where he'd remember that I'd provided him with own gum, and he'd reach into his backpack and pull out his own piece - and even offer me one. Gum does always seem to taste better when it comes from someone else though, huh?
And that is rule 2!