1) If you can increase a resource, play that card. If not:

2) Play a card that lowers the enemy resources. If you don't have one, then:

3) Build your tower. If no blue cards:

4) Play a wall or beast card, whichever you have more of.

When you only need a small tower, build up your tower while inhibiting the development of your opponent's so that your tower will stay higher than their's.  The primary goal remains the building of your own tower of course, then the wall, then destroying the other tower.

When you need a tower of 100 or more and 300 for a resource, focus on your beast production.  Try to keep up your own wall and the tower a bit, but mainly concentrate on destroying the enemy.  After all, it's easier to destroy a wall of 10 and a tower of 5 than to build up a tower of 100!

Basically, once towers are past the 10-20 stage destroying them becomes virtually impossible because the destructive cards are so generally weak. Hence, you should focus on blue if at all possible, supplemented by a little red. If your opponent has a lot of green, he/she/it won't be able to hurt you enough for it to matter. Conversely, if you try to win by destroying your opponent you have to be quick about it or your chances of success are slim.

For simpler games, build up your tower and try to destroy your opponent's.  For harder games, build up resources first and try to build, attack and defend.  After a while, you'll realize that your resources have increased dramatically and then it's easier to win through your resources.

The computer is very focused on wall building. I always make sure to keep the difference between our walls to within 10 points. This may be frustrating at times, but it denies the computer an advantage it works very hard to achieve by building a dominant wall. If you follow my plan, both sides will generally have either no wall, or two very large walls.

I almost never concentrate on walls.  In MM8 you have a card that switches walls. Do you know how much fun it is to see your wall of 1 being switched with the enemy's wall of 57? *GRIN*

If your opponent has a lot of a particular Resource, it may not have any of those cards to play, or it may be saving up to play a hi-cost card, or it may be going for a Resource Win.  By watching the cards played and the progression of the game you'll be able to discover your opponent's strength or weakness.

If your opponent has a lot of a particular Resource and a high Generator to go with it, then you must defend against a possible Resource Win.  If the Generator is not especially high then your opponent either doesn't have the cards to play or is saving up to play a powerful card.

If the Resource is Bricks, you can try to demolish your opponent's Wall to get a response.  If your opponent starts playing smaller red cards then you might have put off a stronger attack.  If there is no response then you will have uncovered a weakness which you can exploit with your green cards.  In MM8 you'll want to have at least one red card in reserve in case your opponent plays the Switch card.

However, if the high Resource is blue or green, then you need to be prepared for the worst and not leave yourself vunerable to the effects of a devastating attack.  If you suspect that a powerful blue card will be played, lower your opponent's Tower and/or build up your own.  If you anticipate a powerful green card, bolster your Wall first and then your Tower.

...there's always a chance this is the resource that he either really needs or wants. For example, has it ever happened to you that you have a hand of green cards, and your dungeon generator is at 1?

A sign of this working is when your opponent starts discarding a card instead of playing one.  This is particularly useful in the longer games and may enable you to switch from the Resource Win to the Tower Win if the cards are kind.

Usually only successful when the victory conditions are low -- ie, the first tower to reach around 75 or lower.  Focus on tower building as well as your wall, but place more on your tower.  Without a strong wall, your opponent can easily damage your tower heavily during the very last moments before reaching victory.  Push up your bricks and beasts resources, then magic.  Use the beasts cards to keep the enemy tower at bay, magic to build and destroy, and bricks to build.

Cards with "play again" are a big bonus here, since they give one an ability to attack or increase resources without turning aside from the main goal - building your tower or destroying your enemy's.  When playing attack, though, you have to pay close attention to your resources.

In my experience, Annihilation is only possible as a quick win. If it drags out, you'll never get away with it.

But in scenarios that start out with small towers and walls, a quick Annihilation Win might be possible, but you need a good attack card to start with.  Your opponent rarely gets back from that.

This option is not advised if your cards are not guaranteed to hurt the opponent bad.  Also don't play this when you start with a wall of 15 and a tower of 25; it will take too long.  By the time you're ready to deliver a final blow, the opponent may have the chance to play a power card (ie, +20 Tower, Wall, damage).

Sometimes it's possible to switch to an Annihilation strategy in the middle of the game when you notice that the opponent's going for a Resource Win and isn't paying attention to his/her tower.  If you feel that the tower and wall are low enough compared with the Beast cards you hold, you can start an attack on the tower.  But again, it must be a swift assault and you need to strike hard or the opponent will overcome your assault.

To counter Annihilation, build up your wall and tower and try to remember which cards the opponent has used.  After he's played a few power cards (Dragon, etc) he's not likely to have or be able play more of them.  If your tower and wall are sufficient, play some damage cards yourself.

You go for the kill early but, rather than making a strong death thrust, you make slashing attacks that cripple your opponent and force him to spend time re-building rather than attacking or increasing resource production.  Then you begin to build your own tower but also keep jabbing your opponent to keep him low.  Generally, a 2 to 1 ratio or a 7 to 4 ratio in favor of building will do it.  This keeps your opponent on the defensive (usually) rather than allowing him to attack you which means your tower building goes 100% undisturbed.

Now your opponent will (in longer games) notice this just before you build all the way up and will then hit you with everything he's got in a last ditch effort to stop the win.  If you played this right then he should be low enough for you to let combat ensue and finish him quickly.

For this type win you need to play the add resources card as quickly as possible and concentrate on not using the biggest resource unless absolutely necessary.  At the same time you must try to force your opponent to use his highest resource and keep some wall and tower building going to avoid being totally destroyed.

Take care to manage the special resource card -- the ones that add 2 if this or all players equal greatest players.  If you use these to good effect you should easily get a resource to 10 to 12.  Never hesitate to take a resource from your opponent especially if it is his highest generator.  With a little practice this will get easier, but there are some times when the opponent will get all the resource cards and he will do the same thing to you.

First, if the computer has an advantage on a particular resource don't hesitate to use "subtract from both players' generator" cards.  This will lead to longer play so that you'll have more time to change things in your favor.

Also, save cards like "+xx to tower [,play again]."  If you collect enough crystals and have the cards, maybe it's time to switch to the quick Tower Win strategy.

I usually go for the bricks.  A lot of fun!