I can share a couple of principles with you that I have developed over time:

1. Store batteries around 40% charged all the time unless you are using them. I do this mostly by simply not charging them after my last flight of the day and they seem to be around 40-50% charged which is good enough. I then charge them up the night before I go out flying. Store them in a cool place. I aren't obsessive about this, if I happen to charge up a pack and dont use for some reason I just leave it charged and use the next time I go out.
2. Warm batteries to around 30 deg c (85 deg f) before flying them, the lower the ambient temp the more critical this is. It is amazing how much lower the delivered voltage of a pack is when cold I also believe it shortens the life of the pack.

I have a attached a picture from www.batteryuniversity.com that I think is useful showng the deterioration of capacity of a LiPo over time based on storage capacity and temperature. I think it is quite instructive.