I don't know
You need a Socrates kind of attitude in the sense that you allow yourself not to know. There's another word for an attitude of not knowing, it is called wisdom. You cannot learn the things you already know, only the things you do not know. This is why questioning is so important, it opens the mind to go on a trip of discovery. It takes courage to say I don't know, because not knowing can make you feel insecure and inferior. This is the paradox, you have to be confident enough to let yourself be insecure for you to be able to be creative.
Be open for inspiration and recognize it
Follow rule number 1. And then realize that everything can trigger a beginning of an idea. Your brain associates all of the time, making new connections is second nature to it. These associations between different frameworks of reference might be interesting. What is interesting to you is felt by you and is not a scientific fact. Therefore it is important that you're in tune with your body and mind. If you're not paying attention you might miss the inspiration. This is something you will never realize, because you have missed it, you might have been to busy with your precious, your mobile phone.
Collecting knowledge and experience
Throughout your life you will do up knowledge and experience. Many artists walk around with a notebook, just in case something interesting comes by or happens, so they can write it down. There are two ways of collecting knowledge and experience for the use in a creative process, indirect and direct. Indirect collecting is just collecting for the "fun" of it, which information might turn out to be useful in a later project. Direct collecting is collecting for a specific idea you're working on. All your knowledge and experience builds up mastery in a certain area, which will give you more room to play. At the same time you build up knowledge and experience you build up routine(s), which makes thinking "outside of the box" more difficult. One way to counter this is to try new things and especially listen to other people, they have a different mind than yours. By following the mental framework (thoughts) of someone else, you temporarily 'escape' your own mental framework. This is a very effective way to think outside of your own box.
Play and have fun with your idea. Try it out in different shapes and forms. Explore as many options as you can think of. If you play with friends, make sure you give each other constructive feedback. We only play when we feel safe and we trust the situation. Anger, shame, shyness and such feelings kill play. Playfulness, being playful is the most important skill for being creative. So taking yourself and others too serious is not an option. Have an attitude that your the greatest human alive and the most ignorant human at the same time. Serious play. Remember, when playing everything is okay, this is not the period to judge yourself or others.
This means keeping the solution you're looking for open as long as possible. This also means you need to think and decide for yourself, when a certain decision has to be taken and make the decision no sooner than at that moment. For the creative person uncertainty is his best friend. How do you know that you're uncertain? Quite simple: you need answers and results to the project you're working on right now. You're in a desperate need for results and closure. Please realize all creative people struggle with this, this rule is easily written down by me, but it is very difficult in the execution. Past failures can make you feel even more uncertain. What you need to keep in mind is that failures is another word for learning. Success can make you forget to learn. And don't forget that you can learn from your successes as well. So a little discomfort might be just the thing you need. Don't take the fast lane because you're afraid to fail, the longer you're able to hold that discomfort the more likely you will end up with something more beautiful and original, at minimum for yourself.
Creativity is learning while you're doing. If you have ideas for a story, write it down. If you have ideas for a new chair, build it. If you have an idea about a service, do a role play. And as long as you find your idea interesting keep improving and upgrading it. Like a person can learn and grow up, so can your project, product or service. Without seed no flowers or children will come to life. See developing ideas as sperm, most of them won't make it. Be wise and try as many things as possible. And when your seed hits the bullseye, don't forget to take good care of it in order for it to grow and flourish, before going out into the world.
Don't do the work
This feels counterintuitive. How can you progress your work by doing nothing. Even better, doing something completely different for some time. The more you focus on your work the narrower the mind gets. In the beginning this is very helpful in executing the idea to perfection, but at a certain moment you will get stuck. No new ideas or perspectives come into your mind, you need to zoom out. Take a break to widen your focus. By relaxing your mind you will give it the opportunity to come up with new ideas and make new connections. You can create a fresh perspective by creating distance between you and the work. You will have to learn yourself to zoom in and out of the work you're doing to get the most creative outcome. Note, that even when you're relaxing your mind it will keep on working on your project without your direct interference.
Organize your creative process
Before organizing a creative process think of possible things you need to do to be as creative as possible. For myself I have identified eight major themes which I need to take care of: Meditation, Inspiration, Organize, Collect, Research, Play, Execution and Switch. These themes have subcategories, namely:
Meditation: bringing back attention, choose where to focus your attention, follow your thoughts, follow your feelings, follow your senses, let everything get into your mind and emptying your mind.
Inspiration: everything can trigger, via an assignment, via a question, via a problem, being open to receive, paying attention and catch it.
Organize: space, time, help, materials, save environment (comfortable and trust) and activities.
Collect: knowledge, experiences, feelings, energy, of yourself and others.
Research: different perspectives, contradictory thoughts, connect different points of reference, analyze, compare, select and organize feedback.
Play: fun, explore, try out, playing rules, play together or alone, curiosity, imagine, role-play, build prototype, move your body, use your voice and write/draw something,
Execution: decision, result, success, failure, improve, maintain, restart, cancel and learn.
Switch: perspectives, environments, styles, shapes, (creative) processes and disciplines.
This is not a complete list. And not in every creative process I have does every item on my creative list gets used. But, the more I understand separate stages (not linear) of a creative process the more I can use its full potential. You do not need to organize everything beforehand, but the structure you have set up should be flexible enough that it can incorporate what is needed. You want to set up a structure which can support your creative process until its completion.