I never really understood cues. Or maybe I did but didn't realize I was doing so. I just sort of guessed.
I tried to feed every couple of hours during the day. So if it had been a couple of hours and he was cranky, I would try food. At 9 months I might even try actual food, especially if he recently slept and I didn't think he was tired. If I thought it was probably close to nap time or evening, I might try feeding a bottle (or nursing) and then settling him down. I don't know, I guess I just tried a few things. I do remember thinking, "This is going to be so much easier when you learn to talk and can tell me what's wrong!" That is true to an extent, but sometimes they don't know what's wrong, either :-)
I was a SAHM when my boys were little, so I had the luxury of not needing them to be on a "schedule." I just tried think, hmm, how long has it been since you last ate or last slept, or maybe it's time to read a book. I just kept trying things until something seemed to have an affect.
To this day (and my boys are 8 & 11), if one of them gets crabby I ask them if they are thirsty or hungry. It's amazing how much food can effect a person's mood!