For me, it's always been discipline and variety. I work in IT and have a degree in Fine Arts. I make films, make interactive sculptures, and write. Staying creative while having to keep a work and family schedule can be quite challenging. This is a problem I encountered when I was freelancing (too busy to so something creative) as well as when I'm following a more regular (too regimented to be creative) schedule.
Throughout it all, I always make sure to allocate at LEAST two hours a day to be craetive. Whether it's free-writing, sketching, editing, or doing something that inspires me (e.g., I specifically selected the two hour block to allow for watching films), I have the discipline to spend at least two hours feeding my creativity--and "feeding" is very broad.
Second, I employ variety. I try to never do something on two consecutive days that relate to each other too closely. For instance, this past weekend, I was fine-tuning an Arduino program to control sound and light timing on a sculpture. Monday, my creative time was spent reading Lucretius' De rerum natura (from a paper book, nonetheless). That's about as far away from technology as one can get, and Epicurean philosophy is an important theme in an upcoming film, so I'm devouring that right now. Tonight, I'm planning on completing a CAD drawing for a custom part I need machined for my sculpture. Everything feeds my creativity, and even if my creative time becomes a routine slot in my schedule, the variety of experiences and, for me at least, planning those experiences in advance, gives me something to look foward to, breaking up the monotony of the timeslot.
End result is that I'm always using different parts of my creativity. Sometimes verbal, sometimes physical, sometimes visual, sometimes sonic, and I find them inspiring and informing each other because of the almost psychotic melange I create.
I also find it interesting to surround myself with other creatives that can share in the excitement of ideas. Other viewpoints and opinions from creative people can be inspiring as well.
At work, my creative outlets are minimal, but I relish them. Whether it's a new UI design for a web page, writing technical documentation, optimizing code...I try to break it up and create variety for myself just to keep everything fresh.
This technique's been working for me for almost two decades, and recently, I realized I was in good company when I ran into this article.
Some of those techniques may work for you. Good luck!