Rituals are one of those things that, much to my surprise, have not gone over all that well with a great many people who play D&D4e. If you look or ask around, you find a lot of people who are happy with it. However, you’ll also find more than a few who don’t like it for one reason or another. I’ve seen a lot of reasons given, some of which I entirely sympathize with even though I’m generally a fan of rituals as presented in 4e. So I'm going to address some of the ones I've seen and see what advice, information, and house rules I can give on the subject.
One of the things that I see most complained about are the costs of ritual casting. Not only for buying the rituals themselves, but for the materials needed to cast them. Not an unfair assessment. Rituals themselves can be quite expensive, especially as you advance in levels and get access to new ones. Further, nearly every ritual casting requires some amount of ritual materials which also cost money. For most players, spending money on these things directly takes away from the money available for magical items like weapons or armor. How can this be remedied?
As a DM, it’s not hard to encourage more ritual casting by giving out scrolls or books with rituals in them. Don’t give them out strictly according to the treasure parcel rules, just throw in one or two per level. Finding materials also shouldn’t be really hard. If your players are wandering around an abandoned wizard sanctuary, who is to say that they can’t find some things that would work in an Arcane-based ritual? Or trekking through the wilderness finding a few gold worth of materials for Nature-based rituals? Another option is to just cut prices all across the board. If everything costs half as much (or whatever you decide), then players don’t have to devote as much money towards it. A third option is to rule that some ritual materials are reusable. Yet another option would be to allow players to spend a healing surge to reduce the materials cost by some amount. However, as a DM you have to be aware for the potential for abuse. Generosity in giving out rituals and materials should only reduce the additional financial burden on a player to encourage them to use the feature more often. If they're abusing it or still choosing to ignore the use of rituals, the benefits should taper off.
As a player, your options are more limited. Talk to your DM, explain the problem, and suggest some of the solutions that I’ve presented above. Creative roleplaying or problem solving may also encourage DM generosity. If you act out your character’s prayers to Bahamut for a Religion-based in an interesting enough fashion, maybe the DM will not expend materials or even say that Bahamut is impressed with your devotion and grants you divine knowledge (i.e. another ritual). Or maybe you hand drew the Arcane circle and symbols that your character uses for a particular ritual. The DM could then say that during the prep for the ritual, your character has gained insight into another way to twist the arcane fabric of the universe. Or maybe you make a pesto sauce to bring to the game and shamelessly use it to bribe your DM by saying that it represents the herbs used for a certain Nature ritual. Use your imagination and see what you can get out of your DM. Even if you don’t get anything out of it, it would make for a more unique and interesting gaming experience.
Most rituals have at least a 10 minute casting time and many have much more than that. While in a town or village, or even sometimes out in the wilderness, this might not be a tremendous concern. But player groups who are in the middle of a dungeon full of creatures who want to kill, enslave, or otherwise do unpleasant things to the PCs may feel that they shouldn't sit in one place for 10+ minutes at a go. This goes double if the PCs are under a time constraint. If they have 2 hours to find and capture an assassin before he poisons the king, there's a good chance they aren't going to want to spend a good chunk of that time on a ritual casting. Even an otherwise useful ritual might be passed over because the players are in a bad place or have a deadline to follow.
So what can you do as a DM if you find that players are passing up opportunities to use rituals? Especially in situations where it would have been interesting or useful? First, remind them about their rituals. Some players, especially if they haven't been using them very often, might even forget they have them or they might forget which ones they have. Second, try and give them a chance to use their rituals without being interrupted... too often. It's exciting to have to try and cast a ritual under fire, just look at all the delves and adventures where your PCs have to disrupt NPC rituals. If you turn things around, you may have a memorable encounter as the PCs try to hold off bad guys as someone desperately tries to finish their casting. However, if you do it too often players may feel it's not worth the effort. If players make a reasonable attempt to hide themselves away where they won't be stumbled upon easily, let them have the time they need. Make it tense and seem like they're about to be set upon at any time (have footsteps come near, then move elsewhere for example), but let it pass.
If that's not enough, what are other options? Time to break out some house rules. Halving or otherwise reducing the time needed for most rituals might some of the problems players have. You may not want to do this as a blanket method across the board for all rituals, however. You may allow other methods of time reduction. Players may be able to trade more powerful effects for reduced casting times, to give one option. For example, maybe a ritual requires a minimum DC of 15 to take effect and then is more powerful with a roll of 20, 25, and 30. If the player rolls a 22, maybe instead of the more powerful DC20 effect, he can choose to take the DC15 effect and reduce the casting time by 25%. Another option is to allow a PC to spend a healing surge to reduce the casting time, representing exhaustion from the effort, reckless handling of arcane energies, or even some sort of blood sacrifice.
Another method is to allow a ritual to be cast in advance. Not perfect, as it means that players have to guess as to what might be useful, but I personally like that sort of uncertainty. One idea I'd had would be to allow a caster to have a number of "prepared" rituals based on tier. 2 for heroic, 3 for paragon, and 4 for epic. This could be easily adjusted up or down depending on what a DM feels is appropriate. These rituals would still cost the indicated time and materials, but then could actually be invoked later (probably with a Standard action in combat). Another suggested method is to have each prepared ritual require the spending of a healing surge, representing the effort that holding on to such primal/divine/arcane energy can have on the body. This one bears close DM watching and may need to be combined with the earlier tier-based limits. It would be very easy for many ritual casters to put themselves dangerously low on surges with even a small number used for rituals.
What can you do as a player to help with the problem? Still not a lot, I'm afraid. Talk with your DM about the problems you're having with rituals or the things you'd like to try. I'm not sure that roleplaying above and beyond would really be of help as it is with the costs, but it may be worth a try depending on your DM and his or her willingness to play along. From an in-character standpoint, if you or your group has to use a ritual, try and do so in the most secure or hidden place you can. Depending on the ritual you want to cast, it may be worth retreating temporarily so it can be cast with less chance of interruption.