I'd like to point out that one should try to raise one's attack and defense levels on one's troops when it is financially possible to do so. Leaving your troops at a basic level and encountering a player who has five times the attack strength that you do can be quite horrifying.

You do need a Training Guild to raise these levels, you won't see the options unless you do. Getting to Expert Attack and Expert Defense isn't cheap, but you get super-troops for your money. As they level up on their own achievements they become even more formidable.