My advice would be to incorporate it as part of your everyday life. Cycle to work, if you live far, get a battery assisted bike. I am a massive fan of yoga as well, the general and core strength you need for that is incredible along with keeping your body limber (which helps fighting injuries and just generally helps with people sitting a lot).

Get in a pool and just go as fast as you can, for as long as you can. Take a short break, repeat. Do this for 15 minutes a day and you will experience a massive difference in your life. High intensity training is very good and a pool exercises a lot of muscles, great cardio and very little strain on your body.

Aim for 20 minutes each day, 5 days a week.