I'm not a fan of New Years resolutions. The problem is they imply that the reason for the resolution is the 'New Year', and not the fact you wish to improve yourself or the environment around you. In my opinion, new behavior starts from an intrinsic motivation, and if it isn't it's doomed to fail. That said, timing around the New Year is great to post a few ideas.
I've tried several different ways to tap into creativity and I have perspectives on many others I have yet to try. First and foremost I belive creative inspiration can be uniqe for each artist. Muses range from joy, to lust to fear and all spectrums between. I'm not talking as much about your muse than I am talking about the ability to have the clarity to communicate between your muse clearly and efficiently. Sorry, there great exercises to enhance the discovery of design, but there are no tricks to 'getting' good ideas.
Meditation:
Meditation was the first tool I used to tap the muse. When I started on my own, my mind was clouded with running a business, and being on my own with no safety net. I spent much of my time designing also worrying about the future. The anxiety of being an upstart was clouding my clarity for the task at hand. Meditation saved me.. It's powerful. Clear your head, lose the noise, and watch for the slightest sparks of information. Although, I'll admit most meditation is about clearing all thought, so I the term is a bit of a misnomer in this case, but if you can use the same skill to clear all noise around your idea the resulting clarity helps. Use it to relieve or silence the stress of the moment so you can move forward.
Drugs:
I know a lot of guys who smoke or 'other' to 'get ideas'. The notion is not for me for professional efforts. I personally, don't want to get myself into a spot where I think something else 'tells' me ideas. Frankly the ideas are already there, they are just very quiet.. My opinion is that if you let your guard down and silence the mental noise you will hear the idea. Smoking is just a shortcut to to let your guard down. Also, what happens when your in the middle of the board room, and the CEO asks you for a new idea.. might be tough to light up to get ideas real quick. I'm very wary of changing my motivation to anything that is not intrinsic. Heavy reliance on other stuff in my opinion is using a crutch. ..not that it's totally off the table as an exercise, but it should not be the 'way' you work.
Booze and drinking. I know a lot of guys who ideate over a few beers with folks. I've personally done it a ton of times. Lots of early stages for projects are born in the pub. In some cases it works, although it's most likely a shortcut for 'guardless collaboration' that gets the job done in this case. Fostering an environment that rewards open collaboration is as good as a few pints, and when your done, you can actually go back to work with some motivation.
Nutrition:
My latest observations have been while watching my nutrition. I've been eating paleo style and I found the ability to see how each type of food effects my energy and mood very powerful. You would be amazed at how much of a hangover a slice of cake can give you, if you do not eat sugar for a month. I'm not a nutritionist, and most of my info is gleaned from CrossFit forums or various Podcasts. I can say this, good nutrition has given me better clarity, energy and has slightly improved my cognitive ability.

Pass on Sharp Mind, but try Carlson Cod Liver Oil.
Don't get me wrong, It's not so much that good nutrition is making my individual designs better, but it is giving me the clarity and energy to keep a focus and do better and longer design sessions. For me, what works, is cutting out carbs, eating A LOT more greens than I have ever eaten before (generally in the form of kale shakes), cutting down portions, and exercise. As far as supplements I've taken a few.. vit C, vit D, vit E, Sharp Mind, Fish Oil, Protein, and probiotics. I found Probiotics (via Kombucha) and the Fish Oil to be most beneficial. Kombucha is a great mood improver, and Fish Oil has helped with general joint wellness. The other stuff seemed like fluff or seemed like they were just duplicating what a decent diet would do.
Exercise:
More a general wellness statement than a 'trick' to getting ideas.. A good fitness program helps tremendously with energy levels and clarity. I personally do Crossfit, and found it to have relieved a lot of the annoyances while sitting at a desk all day drawing. Amazingly my wrists feel better. I imagine the bit of Olympic lifting we do that stretches wrist tendons helps a lot. My posture is much better now too. I can sit at my desk, and not suffer the pain from years of slouching. If you have a poor level of fitness and wellness, don't bother with any of the minor changes people suggest. Taking Vit D, may add a drop to the bucket, but switching to a nutritious diet and fitness program will fill the bucket.
Environment:
Do your best to love your environment.. I've worked in warehouses with folding chairs, to the latest and greatest studios with Aeron Chairs for everyone.. I have the most amazing headphone collection.. hahah.. For me I find a distraction free environment of neutral colors 3-4 monitors, dark'ish lighting with loud music works best. Others I know, need to work among images and toy collections. Some need the womb of darkness and silence. The point being that if you can feel like you fit well in your environment, you don't need to think about it allowing more focus to remain on task.
Proof:
Need proof that you are capable of the most amazing and peerless imagery and storytelling on demand? Just look back at your last nightmare, or remarkable dream.. Your brain is capable of filling a convincing, fantastic, environment with all the detail in the world 'on demand' while you sleep. It's amazing we have the ability to see the muse at night while we sleep, but can barely hear it during the day. It's my thought that clarity and the ability to reduce noise will get you closer.
My nightmare is a dreams of amazing space ships I wished I had the ability to design.. then I realize, I did, and smile..
Then I forget what it looked like, hahaha.. but that is another post.