Strategy > tactics.

But the biggest advice about tactics I can give is: stay active. Dynamic play is very important in Diplomacy, especially gunboat, because if you defend passively then the opponent is making all the moves, and he has a possibility of making progress while the best possible outcome for you is sitting there.

Also, it helps to learn the stalemate lines and the exact method of defending them. Make sure that you have a real line and not a pseudo line!

I guess one rule of thumb could be (and I'm not an experienced player, although I did learn this by experience):

always find something to do for a holding unit.

Support hold something, support move, convoy, frustrate a bounce, even if the supported unit is not under any real danger, it could have signaling value to use it for something (if anything, it signals that you're willing to think about the game).

@Gobbledydook - how many real stalemateline are there? So far I saw the one in the med around Tunis, one between south and north in mideurope (like between Austria and Germany and south Russia and north Russia, the one in scandinavia, where one power holds baltic and bothnia and berlin, and the midatlantic thing. And of course, Juggernaut against England/France around Switzerland. Did I miss one?

A few important points to keep in mind...

1. Knowing about openings and stalemate lines can be useful, but it's not vital by any stretch of the imagination. I've played for a couple of years and have done ok despite only knowing the names of two openings and only the vaguest idea of where stalemate lines are. If you don't like to study, don't. Enjoying the game is far more important.

2. Vital point, this. Just because it didn't work doesn't mean it was the wrong thing to do, and vice versa.

3. Don't panic, don't give up, and never stop communicating. Anything can happen in this game, and it usually does.

On stalemate lines, I'd suggest not thinking of them as concrete "lines" as much as there are different permutations of regional defenses that you can mix and match to create lines.

I want to learn stalemate lines ....... and all of the Lepantos, I'm going to try the Blue Water variation very soon.

Standard Lepanto
When playing the Lepanto opening, Italy usually opens in Spring 1901 with Fleet: Naples—Ionian Sea (to prepare for the convoy to Tunis), Army:Rome—Apulia (preparing to be convoyed), and Army: Venice HOLD (to conceal Italy's intentions and protect against a stab from Austria).

In Fall 1901, Italy then plays Army:Apulia-Tunis, with Fleet:Ionian Sea convoying the army. He then builds a fleet in Naples, a common site for Italian builds. This allows him to play in Spring 1902 Fleet:Ionian Sea—East Mediterranean and Fleet: Naples—Ionian Sea, with the army in Tunis holding. He can then spring his attack in Fall 1902 with Army:Tunis-Syria (convoyed by the fleets in Ionian Sea and the East Mediterranean). This positional advantage is usually fatal to Turkey, as he will likely be under attack by Austria as well. Alternatively the army can convoy to Smyrna in an attempt to outwit a Turkish player attempting to counter it.

@stranger: There are many stalemate lines, but it's just as important to be aware of partial lines and critical squares. For example, as a northern power, how many fleets do you need to hold the MAO against a power trying to break out of the Med? How many units does France need to hold off against an infinite number of Italian armies? One, unless the Munich corridor is open. So, while it's not essential to study a book of stalemate lines, it *is* important to gain a feel for what things are threats and what things aren't.

Another way to put it is that some squares on the board are much, much more important than others. For example, Galicia is the keystone to most positions in Eastern European wars. Similarly, as Italy, in almost every situation I would prefer to lose a center rather than lose control of the Ionian, and if I can't defend everything, I'd rather lose, say, Greece than the Ionian, as long as I have enough fleets to defend it long-term (3 with Turkey in Greece, 4 if you can't stop him from sliding to Albania). As England, losing the North Sea is usually fatal. As Germany attacking France, if you could move an army anywhere from Burgundy, where is the place you'd most like to go? Gascony, in most situations.

One of the mistakes often made by newer players is trading a critical non-center for one non-critical center. When you stab a player and only gain one center, you recognize that was a mistake. The same is true if you blow apart your position in order to grab/save one center.

One last bit of advice, if I might channel Herm Edwards for a moment. You play to win the game. In other words, your goal when you reach the midgame shouldn't be to make sure you hold a line and wait for a draw - it's much better to be too aggressive than too passive, and those are more valuable mistakes to learn from. It's frustrating if you turn a draw into a loss by making a mistake at the end, but with good strategic thinking and aggressive mid-game play, you can learn about stalemate lines from the experience of watching other people hold them against you - always the best way to learn about them!

Blue Water Lepanto
Manus Hand's Fall 1901 continuation of the Blue Water Opening. The Austrian (who opened to the Adriatic) sails to the Ionian in Fall of 1901 to be the victim of an arranged dislodgement by Italian fleets in Naples and Tunis. Austria's fleet then surprises the Turkish player by retreating eastward to form part of the convoy chain that carries an Italian army to Turkey.

Key Lepanto
The Key Lepanto is an uncommonly employed variation of the Lepanto opening. The moves are the same as for the standard Lepanto, but rather than holding, Italy plays their army from Venice-Trieste-Serbia (usually with Austrian support to foil Turkey's Army:Bulgaria-Serbia). The Key Lepanto variation is rarely seen, as it requires great trust on the part of the Austrian player that Italy will not simply decide to stay in Trieste.

It can good to play through a few scenarios when preparing your moves. For this I suggest downloading the program jDip. You can set up maps, enter orders, and then the program adjudicates the turns. (google jDip and you should find it). That's my tip for newbies.

@NigeeBaby: Like in chess, memorizing openings doesn't get you nearly as far as understanding why certain opening have become common. The Lepanto is a good example, and since you've been thinking about it, let me suggest you try and come up with your own answer to this question before some other people give you theirs:

Imagine that Italy and Austria have decided to attack Turkey (and, presumably, Russia; if Russia also wants Turkey dead, there's really no need for subtlety, now is there?). The Lepanto is fraught with danger, isn't it? Italy convoying an army to Tunis runs the risk of getting it stuck there if Austria stabs. In the Key Lepanto, it's Austria taking a major risk. In the Blue Water Lepanto, Austria foregoes Greece, and a critical extra build that would provide one more army on the line against Russia.

So my question for you: Why take these risks? Why is this better than Ser S Alb - Gre, Italy taking Tunis and building a fleet, and then fighting a war with Turkey?

@stranger, you were asking about stalemate lines. Check out this site, it had numerous articles on the subject, with maps showing where they are.
http://www.diplomacy-archive.com/resources/strategy/stalemate.htm

My largest piece of advice is to learn to effectively read the board. There are a large number of people, I've found, that do not have this ability. Reading the board comes down to:

1) looking at the moves made by others (both those that succeed and those that fail). The cliche is that actions speak louder than words, and in this game, it's almost infallible law. People often simply look at those actions of the players near them and ignore those of players that cannot directly impact them in the immediate. If you see the moves made by all of the players, then you can determine the way the board will shape over the years and get a larger picture of what's going on. This is most important in the early years (1901-1903) when the board dynamics are all over the place.

2) Look at the builds and disbands each phase. People build units to suit their immediate need. No one ever builds a unit based on what they'll need two years from now because the immediate need is the most important in gaining new centers for future builds. Armies and fleets have their own capabilities and limitations, and where a build is placed can speak volumes about the direction a player intends on moving.

With the first two, put yourself in their shoes and think "what would I do in this situation?" use this logic to determine why a player is doing what they're doing. I call this 'meta-cognition'. If you can get halfway decent at determining what a player will do based on what they've done and what they have available to them, then you have a lot of power over that player.

3) Listen carefully to what players say as well as what they don't say. A great many people don't want to lie to you, and so they won't, even when faced with a direct question. People will instead find ways to answer the question with half-truths or by simply dodging the question. Knowing what a player is saying as well as what they're not saying can identify things going on around the board.