
Don't let this happen to your pclaim!
TL;DR
This is a very basic list of things you, the hypothetical ultimate sprucecap reading this, are doing right now that will cost you your claim and your LIFE.
If you aren’t a sprucecap, imagine how embarrassing it would be if you did something on this list?! Better read it just in case.
Things in bold are so embarrassing that you will be mocked for doing them. Explanations will be sparse and left as an exercise to the reader to figure out why.

Figure 0: These buttons allow you to see personal claims and village claims. Important!
1. Until you have a wall and claim, you are not safe. Everything in your little trash heap is at risk of being stolen/bashed. This includes you.
FENCES ARE NOT A WALL. STOCKPILES ARE NOT A WALL. NON-WALL THINGS ARE NOT A WALL. They will be bashed, and now your non-wall has a big inviting hole in it. Only a palisade or brickwall work. They need to be covered by your claim.

Figure 1: A lot of beginner effort, moments from destruction. Make a real damn wall. AND COVER ALL OF IT WITH A CLAIM.
2. Your walls should be entirely covered by your claim.

Figure 2: How many wrong things can you identify with this? This image belongs under multiple entries in this list. There were no survivors.
3. It should be impossible to enter your claim without passing through a “Visitor Gate.” You can design airlocks however you want, but all paths into your village should go through at least one visitor gate.
4. Put locks on your gates. Especially if you decided to use normal gates like a FOOL. This is shockingly common. If you do this, you might as well not build the damn wall! Palisade locks (currently) cannot be picked, so just use some wooden garbage locks.

Figure 3: Crimes of convenience.
5. Don’t go outside with your master key. Leave it inside your claim always. Make a wilderness beacon, summon a spare character, and store the master key on them.

Figure 4: Don't let criminal scum get your master keys!
6. Don’t wait several months (and ignore urgent warnings of nice neighbors) to build your walls. An ugly claim and palisade are your first priority. I can’t believe I have to say this.
7. Extend your pclaim/village claim multiple tiles beyond your wall. A reasonable distance. You want to have land claimed around the outside of your hovel for multiple reasons. DO THIS. DON’T ARGUE.
8. Understand at least vaguely how the “Visitor” debuff works. If you have a cave inside your village, have it isolated with REAL WALLS and a VISITOR GATE. “Help, someone used a bug to break into my village”. No, they just walked right in from a nearby cave, through your cave. For homework I’ll let you consider how this applies to mineshafts as well.
A tale as old as time.
9.Everyone wants to kill you. Nationality is irrelevant. Nothing wrong with trying to have relations with your neighbors but if some absolute stranger runs up to your walls and is being nice, why would you trust them? Stop it! Stop dying like this!
10. Be polite to folks. People get bored, and turning your claim into a claim’t could be a fun weekend. This goes double for talking on the forum. If you say something dumb/irritating enough, people will find you based on the variable materials of your cistern and the width of a gate. I know where your shithole is.
11. Don’t stream on a character you care about, or in a location you don’t want attention drawn to. You will die very soon, and the last several hours will have been wasted as far as progression goes. People love to ignore this rule on purpose, even after being warned, it’s so fun. "It won't happen to ME." And you know what? You're right! Go ahead and stream on your main character! I'm sure no one will show up.
12. Don't reveal your coords or any other relevant location information such as Thingwalls. Ever! You really think you can withstand the obsessed boredom of Haven players? Eventually folks get bored, and wrecking your claim could be a fun weekend.
This list is hilariously incomplete, by doing these things you are meeting the bare minimum. Be paranoid against your own claim, look at other’s villages and learn about advanced techniques. All opinions presented here try to err on the side of caution, and assume generic conditions.
More advanced security issues next time? Give away ALL the big boi secrets, maybe?! How to siege Jorb's claim even?!