Some people will tell you the best way to lose weight is through cardiovascular based exercises such as running, cycling or swimming. I tend to disagree with this statement and advise people to change up their training within the weight room. Lifting weights is the best way to shed weight and it's the most effective way because of the amount of calories you can shift in one single session when compared to cardio sessions.
Up Your Game
Personally, workouts of just 8-12 repetitions when wanting to lose some weight isn't going to cut it and therefore you need to mix it up a little. One way of mixing it up is by changing the way your workout is structured and add in different variables of reps, sets and rest times. So, if you have been sticking to the same type of workout for a while now then this is something for you....
When working out it's good to know exactly what you are doing on what day and what week, we call this periodisation. It basically means you don't stick with the same thing over and over again, this is great for seeing results and keeping you from reaching boredom.
One of the best ways I know of increasing your heart rate and work ethic in a session is through increasing your reps per set. Naturally when you do this the weight you are lifting might decrease slightly, but keep in mind you still want to lift a reasonably heavy weight for each exercise. Simply increasing reps to 15 or 20 reps will seriously increase fat burn because you are having to do more than usual.
Decrease Rest Times
If you are used to taking a breather in between your sets then it's time to get uncomfortable with this trend. Changing up your set times is a great way to increase your work rate when training. When you increase your work rate then your overall performance is going to be affected, in a good way. Keeping rests shorter than what you are used to will also increase your fitness and allow you to workout harder in later sessions.
At the end of the day nothing is going to help you change shape better than a solid work ethic and giving 100% in every single session. The only way you are going to see a real difference is when you work even harder than you did last week. Make sure you put everything into each and every session you perform, no excuses ever!!