So here's a tip that frankly I'm not to fantastic at myself. Try and keep a small notebook with you no matter where you go. Something perhaps that can fit in a pocket and you can use to just quickly throw down an idea into. I have a couple notebooks that I use to do exactly that, though I'm not as diligent in actually carrying it as I should be. Inspiration is extremely fickle, in the very best of times. There will be days, weeks, or even months that ideas will just come to you without stop. On other occasions though, not so much. But you can't always just sit around waiting for inspiration to strike, and if you think an employer is going to just let you sit around waiting for it to strike you then you're out of your mind. A notebook though, should be able to at least catch those moments of inspiration the best you can. Maybe every idea won't be exactly what you need but they very well lead to an idea that you can use!
It should perhaps be stated first of all that I'm not the most physically fit individual you will ever meet. I'm really not huge by any means, but I'm frankly I'm happy with myself. With my career path being what it is, it means that I will spend the majority of my time in front of a computer and there are some would use this as an excuse to never do anything other than be at a computer. However, the truth of the matter is that every often you really do need to get up. I'm not saying "Go run a mile" or "Start working on those six pack abs" I mean you can if you want I certainly won't discourage you, but at very least you need to just get up and take a little walk. Skipping over the physical health benefits: stretching your legs, helping prevent cramps, reduce eye strain, etc, it actually does a lot for you mentally.