A) OVERLOAD ENEMY TOWER TRICK: a tower can handle 19 attacks, anymore incoming than that and the extra attacks aren't noticed and posted. So you can sneak big attacks in behind 19 smaller ones!
B) RAINBOW ATTACK TRICK: send 1 of each troop type with a load of archers or cats/rams or bals/rams. Each troop is equal to about 1 extra round for your main troops to fire and thus get lots more kill (some confusion on forums whether this works). i.e. 1 ST, 1 MM, 1 Scout, 1 Pike, 1 Sword, 1 Cav, 1 HC, 1 Wagon, and then your main ranged units.
C) KILL HORSES TRICK: send 1 siege with a load of pikes and archers will trigger hv and cav to come out of the castle killing lots of horses. Works if the seige unit you send will set the range (ie. you send Cat and defender only has Bals; you send Bals and defender only has XBows or Archers; or you send same siege they have BUT you have better Fletching level!)
D) KILL SCOUTS TRICK: just like KILL HORSE TRICK, but you send 1 siege with a load of MM. Same conditions about what siege to send apply (you must have better range then target, or send more MM then they have in unit numbers of their best siege).
E) DEFENDING V.S. SIEGE TIP: HC and Cav on defense kill lots of siege, even if you don't win the battle. Against attacking CATs, to win the minimum defending needs to be 320K Cav or 220k hc, per 100K Cats attacking. Nearly all horses will be lost, but this is a good trade-off for build-time losses! Against attacking BALs, to win the minimum defending needs to be 200K Cav or 160k hc, per 100K Bals attacking. Nearly all horses will be lost, and this is about a break even trade-off if HC are used (good trade-off if Cav are used) for build-time losses.
IF RAM's ARE SENT WITH ATTACKING SIEGE, YOU WILL NEED ADD ~ABOUT~ 200K Cav OR 150K HC, per 10K RAM sent, so that horses can kill the RAM in a single round and thus keep losses to a minimum.
F) DEFENDING WITH MM TIP: 2 mill MM will kill 150K bals, and 3 mill MM will kill 150K cats, when MM on defense. Although nearly every other troops will get targeted before MM are, so this works best if it is a MM only wall v.s. siege (minimal amounts of other troops). Of course doing this may open your city to attacks from other troop types, like 200 K HC wave.
G) STACKING COMBAT BOOSTS TIP: you can stack furies and stack skins of different types to increase bonuses (i.e. 50% and 20% attack boosts stack to create 70% boosts; same for defense boosts). UNTESTED.
H) GENERAL TROOP EFFECTIVENESS TIP:
MM to Swords are low-level troops. Archers to HC are mid-level troops. Bals/Cats are high-level troops. Cities defended by low-level troops are best attacked with mid-level troops
Cities defended by mid-level troops (and low-level troops) are best attacked high-level troops.
MM are best used to kill scouts, traps and caltrops
Swords are useless, imo.