How do I reduce lower belly fat for men?

Sorry Gentlemen, you can't spot reduce. You will lose body fat in the way your genetics are designed to let you lose them. If your genetics demand that you lose body fat last from the lower belly then that's the last spot to lose fat.
But this needn't dishearten you. You can speed up the process by following a simple regime of dieting and exercise. Nutrition plays a very important role in fat loss and getting lean, so pay some attention here. Also, exercising will increase that rate at which your body burns fat.

1. Workout to build muscle - This will ensure you have more metabolically active tissue to increase energy consumption in your body thus enhancing your BMR. Engage in  comprehensive bodyweight training as this will build muscle and regulate fat loss like not other training method can.
2. Eat small meals more often - This triggers a message to your brain that you need not store energy in the form of body fat as there is a continuous supply of calories coming into the body.
3. Curtail excessive insulin release - This is a hormone that triggers fat storage, especially when the blood has high sugar content and high saturated fat in the diet. You can avoid this by increasing your comlex carbohydrate intake, protein intake and fiber intake. Also have more unsaturated fatty acids - they tend to be rich in Omega-3s that help enhance muscle cells insuling sensitivity, thus reducing fat storage.
4. DO NOT CONSUME CARBS BEFORE BED - Let the last meal that you consume for the day be devoid of carbohydrates. This enhances growth hormone production and release while you are sleeping. This was the greatest change that helped me lose 20 lbs in 17.5 weeks and I actually leaned out on a simple calisthenics program at home while also putting on muscle.