Ryven has an excellent point. Sometimes, your best bet is to go ahead and make a guess. It eliminates possibilities, which is SUPER valuable in this game, and it also helps give the FS a strong sense of where the clues they've given are leading the players. Often, if a FS seem hesitant to give a clue, it might mean that they're worried more information will only cause players to stray from the path they're already on.
It's always fun to be the one that actually guesses the right combo, but it's just as important to take chances and whittle down the possibilities. Plus, as badass as it feels to catch a murderer, you feel like a real pro when you do it in 2 clues, even better if you're not the witness but they think you are now after pinning them so quick.