Although Neon Genesis Evangelion was made as a deconstruction of the genre, it ended up becoming one of the codifiers for future series. So, what do we need to make a formulaic mecha series? (Originally written while TV Tropes was having trouble)
1. A name for the series mecha.
2. A theme for mech naming. (I'm thinking I'll volunteer for this: My ACs are named after types of songs, with Aria being my main one.)
3. A mysterious waif and her mysterious origin. (Clone, robot, long lost possibly alien race, takin' all bets!)
4. Technobabble for why conventional military weapons are ineffective.
5. Some religious/artistic/cultural phenomenon from which to draw excessive symbolism.
6. Cause for the main character to have emotional troubles. Level of legitimate angst to wangst variable.
7. Disturbing imagery.