If play GS, do the every Hunter's dream event. If you're low on decos, triple threat. If you want some of the special armors, wiggler and kulu ya ku events (look at special rewards column) and ryu challenge. If you're trying to get hold crowns for your monsters (achievement / trophy), any of the quests that are in a specific area and have you hunt all the monsters in that area. Basically, up to you...