There are some classics, aren't there?
Speak softly and carry a big stick.
Theodore Roosevelt
Diplomacy is the art of telling people to go to hell in such a way that they ask for directions.
Winston Churchill
Diplomacy is the art of letting someone else have your way.
Sir David Frost
The supreme art of war is to subdue the enemy without fighting.
'Sun Tzu', The Art of War
To say nothing, especially when speaking, is half the art of diplomacy.
Will Durant
Diplomacy is the art of saying: "Nice doggy," until you can find a rock.
Will Rogers
Ah, well. Lovely.
Diplomacy, the game, is about communicating. I would love to say we all know that but it's pretty clear that, online at least, that isn't the case. I was once in an online final, playing France, where the player controlling England didn't send me a message in the whole time he survived before Germany and I eliminated him. That's fine, that was his choice. How he got to a final playing like that, I've no idea. But still...
You can get through a game of Diplomacy without communicating with a neighbour, of course. That tends to be in Gunboat. I suppose if the player you're not talking to is inept enough to make an enemy of other neighbours, that would work too. There are players like that out there. Play against me, please, if that's you.
I'm not going to claim I'm the best diplomat ever. I tend to get dragged into philosophical discussions about the game when some fool (dammit, you see?) bangs on that I'm the most despicable thing in the world because I stabbed her. But at least I keep talking. And I also know a game isn't the best place for that discussion.
There are some things to remember when playing Dip beyond the "be a diplomat" one. If you're crap at this part of the game, though, start there.
Another one which ought to be pretty obvious, I think, is don't lie consistently and constantly. I know, I know, it's a game of deceit. But deceit and lying aren't necessarily synonymous. There's nothing wrong with lying if you can do some serious damage by doing so. Anyone who tries to tell you to never lie is probably very good at drawing games.
Lying should be used sparingly. If you don't intend to do something another player wants you to do, then don't say you will automatically. You might be considering it. You might be able to find a way to do it. You might have something more important to do before you're able to help her out. You're only definitely going to go with it (not) if you're going to launch a devastating stab.
And, of course, you may well want to be allied to this player, or to maintain the alliance, in which case be honest with her. You won't do it because... Diplomacy is about being honest with your friends, and deceiving your enemies.
Another tactic is to not mention something. A player talks to you about a number of things. Let's say one of her proposals is something you don't want to happen, but you don't necessarily want to tell her you don't want to do it. In this case, respond about the the other items and don't mention the one you're not interested. If she comes back to it, as she should if it is key to her, then you'll need to address it, of course, but more often than not being positive, or even talkative about some things, while ignoring the other, will encourage her to think you're positive about everything. Deceitful, maybe, but not lying.
What about the reverse situation? You suggest something to another player, probably an ally, and they don't want to go that route - what do you do then?
Well, how important is it? Is it key to success? In that case, argue the point again. If you can't prove that something is that important, then it's either something she really doesn't want to do or you aren't making your argument well.
If it is something of lesser importance, than move on. There's no point in pushing something that is little more than an idea.
In either case, absolutely do not erupt about it. Let's face it, you having a blowout is not helpful, diplomatically. It's annoying to the other player and more than a little pathetic on your part. Act like a brat and you'll be slapped down like a brat (or you should be). I mean, yeh, obviously you're right, but sometimes being right is about perspective. Whatever you choose to do about the situation, and I tend to file it away for later consideration, appear accepting. Diplomacy, remember?
Throwing a tantrum can, occasionally, be useful, although rarely with an ally. OK, never with an ally. I was trying to think of a time when acting like this would be useful with an ally and I can up with ... ... so don't. But with someone you're trying to throw off her game, why not?
Diplomacy, the art of communication and negotiation, is very much about control - self-control. This doesn't mean you can't be provocative, however. I'm not talking Trumpian 'diplomacy': piss someone off, make threats you can't carry out, and bluster when your blust won't raise a blister; it's about controlled play-acting. Nobody said diplomacy, or Diplomacy, had to be gentlemanly! (Well, actually, some people believe Diplomacy should be juts that, but they're missing a trick.)
Provoking a reaction is exactly the same as provoking an action: if it's managed, if it's calculated, it's all good. There are - possibly - limits, but I think they're self-imposed. I wouldn't be nasty about it, personally, because I'm a lovely person, but if I see an advantage in trying to provoke another player to react in a way that is negative to her - and positive to me - then I may use it.
The key word there is "may". What exactly am I hoping to achieve? Will this help my long-term ambitions? Will it give me a real advantage? After all, it may be that at some point in the future I'll need to go back to this person and build the bridges I've burned. For me, it is all about game management and the agility of my plans.
A good bit of general advice that is often bandied about is to maintain communications with the person you've stabbed or has stabbed you. It's possibly easier to do the latter; it could well be that you need to persuade her that she's made a bad choice in stabbing you. And, of course, you may be negotiating for your life! That's some incentive... for most people. Going into a sulk or, worse still, stamping your diplomatic foot and tanting, isn't a good idea. Ever.
But stabbing someone and then getting in contact after you've ended their ambitions (and if you've stabbed and not ended their ambitions, why the hell did you stab?) is tough. Very tough. What's the point?
Well, stabbing isn't always about destroying another power. This is all about game management. You want to end another player's chances of winning the game but you don't necessarily want to eliminate them. This, then, is when you need to re-open diplomacy.
Perhaps giving them some space (STFU) for a time is good. Often, when you've stabbed well, the other player will either be mildly annoyed (do I need to translate that?) or simply not want to talk to you, you betraying bastard. But don't leave it too long. The bridge might be gone, but you can always knock a pontoon together - and you may need it. That power may well be the thing that stands between you and some other player's victory.
Let's be honest, though, sometimes this isn't going to work very quickly... so you'll need to be persistent. On the other hand, some people can see that a stab has been effective or that they've been daft to leave the opportunity, and these people will be prepared to nod, sigh, and re-evaluate. In this situation, survival is an option; if they're able to recognise this, you have a shot.
I've not really looked at the aspect that is so important about diplomacy in Diplomacy because I tend to see this as the key to a game (probably because I'm comparatively weak tactically) but your diplomacy should complement your on-board tactics, and vice versa. Unless you're Gunboating, diplomacy is the pathfinder for your movements on the board.
Plan ahead. If you're moving to capture this SC, you should be looking at how to capture that SC next. How are you going to do that? What units do you need in place where? And - equally importantly - how are you going to persuade others that they need to let - or help - you achieve this goal?
For me, there should be a point to anything you do in Diplomacy. However, that doesn't necessarily need to be to obtain an immediate advantage or goal; it may be that the point is to prepare the way for future goals. This is when diplomacy comes into it's own. What you can't do on the board now you can prepare to do later by starting the diplomacy early.
Diplomacy is the key to this game. You just need to consider which locks to use the keys on.