Do you plan out your mods using pictures? Here are some of mine:

Here is tech tree, I think it is self-explanatory.

Here is my part of my excel sheet for bonuses and detriments for different types of planets.

This is a "planet trait card." Each box is an ExtremeTypeModifier, with prerequisite techs and bonus values. The C12 refers to the curve used to derive the planet class (this one has the usual curve, average is 12). Note that the far right box has an error, the tech requirements are mixed up.

This is a group of planetary systems, lane numbers at the top. Boxes represent 'slots' in a lane: black are dead, blue are habitable, brown are asteroid, and red are gas giants. A circle in a box indicates that a slot is occupied (green means may be habitable). A box with an X means that older systems don't have that asteroid. M/O means only habitable in medium or old systems (darned solar flares in early red dwarfs!).

Do you do anything like this? Please post pictures, they might give other people ideas!