For this cheat, you'll need barracks (any level), army camp (any level) and laboratory (any level).
First, choose a troop to upgrade in the laboratory. Let's say Wall Breakers for instance.
As the timer gets close to running out on the upgrade, fill up your army camps with any type of troops. Then, fill up all your barracks with whatever troop is about to be finished upgrading (in this case: wall breakers).
They will sit in the barracks and not be able to go to the army camp, due to camp’s filled to capacity.
Once the upgrade is completed in the laboratory, sell back the troops (wall breakers) that were sitting in the barracks. You’ll get the upgraded elixir-cost, instead of the cost you originally paid for the wall breakers.
Attack Strategy (Silver I and Below)Added 4 Apr 2014, ID #3994
The most effective way I've found to attack a base is simple. Release some giants so that the defenses are entertained by these cannon-proof though guys. Now deploy some wallbreakers alongside these huge guys so that they make a gap for the giants immediately. Now, release some archers and some wizards along the perimeter of the base and watch yourself getting a victory.
Hope this helped some people who are barely starting the game and are having trouble winning some PvP battles. Add me on the game center/Google+ if you want to clash with me. -Modder_Dude0_0
There are no official cheats for Clash of Clans. There are people who try to hack or exploit the game in order to get free Gems, but Supercell are relatively generous in that department anyway, as they reward you with Gems for cleaning up obstacles in your base and for completing Achievements.
Furthermore, anyone offering you a download or Gems in exchange for your username or password are probably trying to get personal details from you and you should refuse to give them out. The developers work hard for a balanced game, and anyone getting free Gems compromises that - the best idea is to learn how to beat the game using your own tactics that no one else knows about, then you'll have a real advantage!
How to save your elixer when your offlineAdded 31 May 2013, ID #2458
To be able to save your elixer where people won't get that much elixer. Just make sure your camps are full and then fill your barracks up with bombers then you can get offline with like only 100,000 elixer instead of 300,000 elixer. Get back on, then unload your barracks first thing and then you will get all of your elixer back.