1) Workout 30-40 minutes. People have a tendency to think in order to get a great workout you need to do it for long periods of time. I've found that if you plan to workout longer you tend to lower your intensity. Why not increase your intensity for a shorter period?
2) Drink Water. I can't emphasize this enough. The majority of the population has a minor form of dehydration. Drink water at regular intervals throughout the day as water takes a couple hours to absorb properly by your body. Therefore, drinking water just before a workout is not as beneficial as most think.
3) Protein and Carbs. Make sure your muscles get enough building material with easy to prepare protein shakes. To fuel your workouts, make sure you eat energetic carbs like bananas and apples.
4) High-intensity Workouts (HIIT). This form of short duration, high intensity workouts have been really popular for the last several years. Make sure your intensity level is adjusted for your current fitness level. If you are just starting out, be sure to gradually increase your workout intensity until your body can confidently go its maximum pace for a short workout.
5) Compound Exercises. I see a lot of out of shape people focusing on isolation exercises like bicep curls or tricep extensions instead of compound exercises. The biggest benefit of compound movements is that with just a few exercises you can workout your whole body. Plus it more mimics everyday body functions. Great exercises include squats, deadlifts, pushups, and pullups.
6) Mix Up Your Routine. Change up the way you exercise, do cardio or lift weights. I'm constantly changing up my fitness routines as I get bored pretty easy. One day I could be doing a crossfit routine, the next, I could be playing hockey. Variety will help keep you interested.
7) Circuits. I love circuits. Many gyms have a set of equipment set up that you can do in order. If you are running short on time, do a couple circuits of these machines and you could have a total body workout.
In my typical week l set a goal to include 2-3 days of high intensity strength training and 2-3 days of high intensity cardio. All these workouts are typically 30-40 mins and alternate days. The key is to consistently get several short but intense workouts a week. Make sure you eat nutritious meals that help feed your body before and after your workouts. Proper nutritional intake will help ensure you get the most out of your physical activities.