Stuck in the same predicament many times myself, here are some ways that you can get started on your creative project and get your idea out of your head and out into the real world. These have worked for me in the past when moving forward on particular projects.
1. Focus on that one idea
First of all, as creatives we have millions of ideas swirling around in our minds every second of the day. But there are only a few that pull at you, tug at you with a vengeance where you find it impossible not to react. Start there. The others will remain in your 'someday' pile for now.
2. Move from pen to paper
Once you know which project you want to get started on, write it down so you can see it outside of your head and gain some perspective on it. By writing it down, it begins to actualize and gives the idea some life.
3. See where it fits
See where this project fits into your life right now. How much time are you realistically willing to invest in it based on your already-committed responsibilities and duties? Do you see this project as a part-time creative outlet or a budding business idea that has potential to be very lucrative? Sometimes we don't take an honest look at this and get ahead of ourselves and start projects that don't fit into our daily schedules.
4. Gather the goods
Research and collect stuff that inspires you. Create a folder or box and start filling it with pictures, articles, symbolic items...anything that you come across that you think fits your project. In the process, start to observe who is already doing it and notice what you like and dislike about how it's already being done.
5. Put it in the corner
Set your project aside and give it some time to marinade. If it pulls you back, then you know it's definitely time to keep going. The time off will give your mind a break and other information will appear that will eventually be used to fill the box.
6. Talk to someone who's doing it already
Begin to seek help from someone who already has the know-how of your project and who can possibly offer some ideas/feedback on how to get it off the ground. Schedule an information session (I love these) to pick their brains and gather insights.
The key is taking small actionable steps. You owe it to yourself (and the rest of us) to give the proper attention to the idea that constantly tugs at you. Give it space to unfold and run its course. The good news is that whatever happens to the project, you gain valuable knowledge that you wouldn't have gained otherwise.
So please, don't let the gold mines lay around for much longer and get started today.