An on going issue I have is with my players is that they leave a very large amount of power untapped in the arsenal of things they can do, namely rituals.
As a DM I use them all the time, but the party just sort of glosses over them.
I have even taken the step of reminding them during play that they have them but to no avail.
Does the group here have any ideas?
Give your ritual casters magic items that can be used as item focuses with specific rituals. My swordmage had a +1 runic longsword that could be used to freely cast Unseen Servant, and I used it all the time.
Also, specify that a portion of their treasure is ritual components instead of gold pieces or art objects. If they can't do anything with the treasure but use it to cast rituals, they'll be more likely to cast rituals.
Don't worry about it
If your group chooses not to take advantage of rituals, there's no point in forcing them to do something that doesn't seem fun. If for some reason they need to cast a ritual as a MacGuffin, let them know (if possible, in character) that that's the correct solution. Otherwise, ask them why they don't use rituals and create a house rule to patch that part of the game for them.
I suspect the reason is that there is the (correct) perception that rituals take too long and are too expensive. I certainly know I have a hard time spending cash on consumables. If this is their problem, talk to them about what they would like rituals to do and make it so.
Requiring players to take advantage of an aspect of the game they don't like is silly and ruins the fun for everyone.
Two ideas:
Make rituals more available. I've been selling my group discount ritual books. They get excited when they see a deal on an item and are more likely to pay attention to it. This also lets me hand them a dozen or so rituals all at once. Even if they didn't plan to use all the rituals in the books, they may find a use for them once the ritual is in hand.
Confront them differently. D&D players get set in their ways. If a technique works once, they're going to repeat it instead of trying something new. Usually that technique will be "kill it." Sometimes that technique will be "subdue, search, and torture it." The rest of the time it'll be "shout the names my trained skills until the GM tells me what to roll." What you need is a situation where one of these three techniques won't immediately work. If one of them is the obvious answer, the players will use that before they even think of using rituals. But if you surprise the players with a novel situation, they'll look at all their resources instead of falling by to the tried and true methods.
One approach I have seen that appears to work well is to make sure that your game has game play that happens outside of the initiative roll situations (either combat or skill challenges). This can be still in the middle of an adventure but since many rituals take both component costs and time to use if the game never slows down to a timeframe that accommodates using rituals players will likely gloss over and discount the value of them.
But when you give the players situations that aren't combat or the fast pace of skill challenges but do offer situations where rituals can resolve problems suddenly they become more valued resources.
If your players need further hints and guidance you could also introduce an NPC or two who use rituals to benefit (or hinder) the players - sometimes it takes an example to get people thinking of the options.
A factor to also keep in mind, however, is that non-ritual casters should have something to do to further the progress of the game while the ritual casters are spending game time resolving rituals (and/or researching them, gathering components etc).
One short and sweet answer, have the enemy use rituals against the party. Some harmless scrying on them to start. Perhaps have the enemy 'gate' into a fixed teleportation circle. Have them bump into one of those wyvern camp guards (left my PHB at uni, so I can't find the right name).
Then give them opportunities to return the favour. If they don't want to, that's fine there should be equally interesting alternatives, but where it might cost 500gp for components to that teleportation ritual, the caravan is 400-600gp (depending on who you want to 'encourage them')
