A: The most efficient workout (whether we are talking about bang-for-your-buck or ease of fitting into a busy life) is the workout you will actually do.
Your goals, priorities, schedule, commitments, physical ability, climate, financial resources, and personality all play a role into figuring out how to incorporate exercise into your life. And I think this is exactly why a lot of people get stuck and just say, "forget it, it's too complicated".
When I work with people who recognize that they need to start exercising but are unwilling to commit to an actual "plan", we talk about the things they are already doing on a daily basis and figure out ways to make some of those activities a little more active while also considering ways to squeeze out some of their behaviors that are negatively affecting their health.
Walking is one of the best exercises: You can do it just about anywhere, it takes only as much time as you have, and you don't need any special equipment.
This is what I recommend to people who are toying with the idea of getting more active: Go for two 10-minute walks each day. Ideally take one right away in the morning because natural light helps get your body clock on a healthy track and can improve sleep. The fresh air will help wake you up and this is a perfect time to practice some mindful awareness and maybe say a prayer of thanks for a new day. Your second walk should be any time you can squeeze it in. I like a walk after dinner because it helps food settle which is especially important if you struggle with digestive issues. Paying attention to your breath as you walk and how it coordinates with your steps is a simple meditative practice that can calm the mind.
Figuring out how to build new habits into your life is one of the hardest parts of starting to exercise. There is no one-size-fits-all program and trying to copy someone else's schedule without considering your specific circumstances is a great way to get frustrated and feel like a failure.
Be gentle with yourself, be curious about figuring out what makes you tick, and celebrate all the stepping stones along the way.