One Gem Trick [FIXED] Edit
When someone has little money in their treasure chamber, the system will provide a default loot for their base. The size of the default loot provided is dependent, among other things, on the level of your throne room and is increased by roughly 20k every time you level up your throne room. The maximum default loot for throne room level 9 at ~3000 trophies for my level 64 king, is just over 200k for a raid.
Initially, when you log on to do some raiding after not playing for a while, the default loots of your opponents will be quite high and will be the maximum possible. As you farm these default loots, the amount of loot provided by the system would decrease for each successive raid. If you spent gems to refill your silo, however, the default loots for bases would be increased back up to the maximum possible default loots. Since the number of gems that you spent refilling your silo didn't matter, this trick was called the "one gem trick".
The one gem trick doesn't exist anymore, and was removed by Flaregames during a maintenance break towards the end of August 2014. Now the amount by which the default loot is reset is dependent on the amount of gems that you spend on refilling your silo. The more gems you spend, the more the default loot is reset.
Open Base Edit
An open base is characterized by an almost straight path to the castle gate with either no, or only a few towers. Normally, the waves of troops are all present, but not always.
Half-Open Base Edit
While this type of base isn't if necessarily characterized by a straight path to the castle gate, the path structure will still be very poor and there will be no cases of choke points being set up by parallel paths. Most, if not all, of the player's available towers will be used and all of the waves of troops will normally be present. It is essentially just the harder version of an open base.
Trophy Striping Edit
This is the process of using an account whose trophy level is much lower than its natural level would be to remove a large number of trophies from a higher ranked player in a single attack. For example a player might normally play at a 2900 trophy level, but deliberately lose matches to sink to 1400 trophies. He could then attack a 2900 level player and remove many many trophies from that player. This is usually done to annoy the higher level player. See this discussion for more details.