ok, here's the thing: i'm also completely new to working with consoles as the only translation hacking i've done is for PC games the land of milk of honey. No crazy compression systems no crazy special file formats you just sit down, and get to work...
i'm having the trouble right now that for the life of me all the editing i do on a psp game won't show up on the PPSPP emulator when it runs. i have no idea why. maybe it has to do with decryption. in any case for the OP's question:
man, it REALLY is game-by-game. even games from the same company! I mostly stick to STARFISH games (wizardry empire/elminage) and recently i pried open the NDS game by them called Wizardry Asterisk and man was it a shock. i've done some light NDS stuff but i have never in my life seen a more daunting obstacle course for anyone wanting to translate that small game.
apparently to i guess to save space ? they compressed _every_ _single_ _file_ so the normal process of going through every single file and opening it in a hex editor to check for japanese dialog (which is what i recommend you always do first before anything else) and then copying that jap-talk and pasting it into google translate to see if it has anything to do with what you're looking for (i.e. is it a random piece of dialog, or is it text from the game's character creation menu, etc)-- even that whole long, tedious process would take orders of magnitude longer with wizardry asterisk because you have to decompress EVERY. FILE. EVERY FIEL!!!!!!
heh.
i mean at least they're all inside clearly labeled folders such as data, monsters, npc, etc, but i would rather they were all disorganized and NOT compressed....
so i guess the real answer here is: if you are REALLY not sure where the game has its dialog, i.e. it doesn't even hint at anything with the folder names or the file names then do what i do and do it "moron style":
1) open one of the files in a hex-editor, i recommend CrystalTile2
2) use your mouse's scroll wheel (or arrow keys) and literally eye-ball the file slowly, very slowly, until you find a coherent-looking japanese sentence or word
3) copy that and quickly open up google translate on chrome (or whatever) and paste it to see what it says. if for example you do this with 3 pieces of jap-text in that file and they are all references to stuff like mountains, towers, Tsu, ho, et,c than that is actually game code and useless to you.
4) eventually you WILL find the dialog. you WILL. trust me. recently i found a piece of dialog i wanted to find from elminage 2 by starting up the game on the emulator and taking a screen-shot of the dialog; i then went through roughly about 9 different .BIN files in CrystalTile2 slowly eye-balling everything until i eventually found the conversation i was looking for...
on the plus side trust me you will start learning to recognize/read japanese! lol can't be helped if you spend so much time looking at japanese characters and then translating them.