Here's how I find game composer information:
1. First I check the internet. If it's a Japanese game, I go straight to
GMCL ver. 2, which requires some basic Japanese skills to navigate. If I can't find the information there or if the game is of non-Japanese origin, then I try various Google searches.
2. If nothing comes up, then I use Chris Covell's ROMSearcher utility to do a relative search for text in the game (I do searches on 'SOUND' and 'MUSIC'). If nothing comes up here, then...
3. If the game is non-Japanese, I give up and put <?> in the composer field. If the game is Japanese, there is still the possibility of credits using kana/kanji for the composer name. I gauge the feasibility of getting to the end of the game, noting what type of game it is, how long/short it is, and how easy it is to hack/cheat to get to the end as fast as possible. If I see the game as too long or too Japanese intensive, then the composer field gets a <?>.