I've read a lot of articles on player vs. character knowledge, where the crux of the article is always that players know more than their characters, and metagaming is an issue. For good or for bad, I have the opposite problem. My players don't study the source material, and are effectively blank slates. This means that even if their characters would have a piece of knowledge, the players certainly don't.

We're playing Rifts, so there's a lot going on. Tons of skills, magic, psionics, tech - a lot for a player to know, even if they're only concerned about what their particular character can do.

Generally speaking, how do I impart knowledge to the players that their character would know, without "giving it away". Ex. the party was prepping for a delivery into hostile territory. The Shifter (mage) in the group should have gone to the magic store and bought some scrolls that might be useful. But the player of the Shifter isn't really aware that scrolls are a thing, and doesn't have all the spells memorized so wouldn't even know what spell scrolls to buy. As the GM, I know both of these things. How do I give that knowledge to the player without saying "You should go buy some scrolls of x, y, and z spells"?