how to lose a beer gut?

As a general rule of thumb, no refined carbs after lunch. Just protein and vegetables.

30 minutes cardio a few times / week with your heart rate in the 120-140 bpm range. 

The Good Protein Chart

Protein can help you shed those unwanted pounds and keep your belly full. But it's important to eat the right amount and the right kind of protein to get the health benefits.

Fish & Seafood

Seafood is one of the best sources of protein because it's usually low in fat. Fish such as salmon is a little higher in fat but it is the heart-healthy kind: omega-3 fatty acids.

White-Meat Poultry

Stick to the white meat of poultry for excellent, lean protein. Dark meat is higher in fat. The skin is loaded with saturated fat, so remove skin before cooking.

Milk, Cheese Yogurt

Not only are dairy foods excellent sources of protein but they also contain valuable calcium. Choose skim or low fat dairy to keep bones and teeth strong, prevent osteoporosis and enhance weight loss.

Eggs

Eggs are one of the least expensive forms of protein. The American Heart Association says normal healthy adults can safely enjoy an egg a day.

Beans

One-half cup of beans contains as much protein as 3 ounces of broiled steak. Plus, these nutritious nuggets are loaded with fiber to keep you feeling full for hours.

Pork Tenderloin

This great and versatile white meat is 31% leaner than 20 years ago.

Soy

Twenty five grams of soy protein daily can help lower cholesterol and reduce the risk of heart disease. Combine soy protein foods like tofu with a healthy low fat diet.

Lean Beef

Lean beef has only one more gram of saturated fat than a skinless chicken breast. Lean beef is also an excellent source of zinc, iron and vitamin B12.

Protein on the Go

Grab a meal replacement drink, cereal bar or energy bar. Check the label to be sure the product contains at least 6 grams of protein, and is low in sugar and fat.

It don't think it matters.  If you do the cardio intense you will probably be too spent to do weights though.

What's trendy now is the P90X routines where you basically do high intensity pushups/pullups which also gives you cardio.

Sorry about the girlfriend.  But now is the best time of year to get in shape though.  Pool season almost here and when football season hits, everybody will be back to drinking again.