I'm a little confused about how to use spells effectively in Elder Sign. I understand that you play the spell before a task roll and then you can set aside as many dice as the spell has icons, whether you succeed or fail at the task. When is the best time to use a spell?
Is it mandatory to place dice on a spell once you've used it? Do I have to place a die even if it doesn't help me on the task in any way? If you don't get any icons that help with the task, then it seems like you are 'locking' a die, which is a big disadvantage.