Here's a packing-list of some suggested tips, tools, and techniques. As always, take what you need, leave the rest:
1. Don't be an "angry vet." If someone randomly thanks you for your service, or welcomes you home, say "thank you"—even if you don't feel like it, even if you're "not a hero," even if you were just doing your job and happy to take the paycheck. If nothing else, say "thank you" on behalf of your buddies—particularly the ones who aren't there to take the praise themselves. You know who they are. You know where they are. Be humbled that someone in this allegedly grateful nation still gives a @#$!.
2. Avoid initiating unnecessary friendly-fire missions. If you see some rag-bag who's wearing a uniform that looks like soup—so that he can get a free sandwich or cookie, no doubt—use good judgment before you engage him. In fact, maybe you don't need to confront him at all. He might just be legit. He might be homeless. He might be mentally ill. Everybody has their own war. Don't make others' any worse.
3. Don't assume that women aren't veterans, too. You know better.
4. Dine responsibly. You don't have to take every deal and discount. Think hard about accepting gratitude, particularly when it comes from faceless corporations. Don't reward people who pencil-whip their patriotism. Freedom isn't free, and neither is lunch. Bonus tip: Remember to tip your waitstaff, regardless of how much money you didn't pay for a meal. After all, they're working on your holiday. Thank them for their service.
5. Don't get into any bad-humored urination competitions. That includes jags and jihads such as "pogues vs grunts," "geeks vs. jocks," and "whose deployment sucked more." You know better.
6. Look for teachable targets of opportunity. If someone asks you about your service, have a short and courteous answer prepared. If a child asks you why you're wearing a poppy, stop and talk with them. If someone doesn't know the difference between Veterans Day and Memorial Day, don't make them feel bad when they ask for clarification. Tolerate unnecessary apostrophes. Be polite, be professional: You still represent the tribe, even if you no longer wear the uniform.
7. Check in with a buddy. Back in my day, we didn't have "battle buddies." We had "bunk buddies," until people figured out how stupid that sounded. Having a "battle" or "Boot Camp Friends Forever" or whatever doesn't sound much better. Now, I don't care what you call them, but it's time we start a new tradition: That guy or gal with whom you spent the worst and best days of your life downrange? Call them this weekend. Do a radio-check. See how they're doing. Compare notes. Count your mutual blessings, wounds, or remaining ammunition. Ask if they need anything, and if you can help. Most of all, however, tell them thanks. Because, coming from you, that still means something.