I know that fares can change, but is there a general rule for finding the best fares? I'm specifically interested in fares to Europe.

I've been checking fares for LAX to FRA for the last 2 months (3-4 months ahead of my scheduled departure) and they were all around $800. Then this weekend (about 2 months ahead of scheduled departure), those same flights' fares dropped by over $200 (and they're still up today).

My friend told me that airlines keep their prices high until 1-2 months ahead. Is that true? From this situation it is, but I'm not sure if it's just a coincidence.

I plan on taking more (personal) trips to Europe so I'll need as much help with finding the best fares! Thanks!