1. Generally, lift with your knees, don't carry anything too heavy, etc. Two months after the c-section your muscles should be on the mend unless you had particular complications during the pregnancy or the operation. Use common sense, if it hurts don't do it.
2. Diet, exercise and hope that you have good genes. It also depends a fair bit on the condition you were in before your pregnancy and how active you were during the pregnancy. The diet and exercise part should be tailored to your particular physical condition and caloric needs - if you're breastfeeding you don't want to limit your caloric intake too much! There is very little evidence supporting the usefulness of all the weight loss wraps, creams and massages on the market, but some people will swear by this or that. Some simply sap water out of your system for a few hours so you appear thinner. There is no quick fix that I've found, you need to put the work in and be realistic about how long it will take.
3. Your doc should clear you for exercise at one of your postnatal appointments (I believe that it was at just about 2 months that my doctor said I could resume any exercise program that I had been doing before, but start out slowly). If you have any particular concerns (or if anything hurts/ doesn't seem right) talk to your doctor before starting anything. There are all sorts of postnatal work out programs as you note - yoga, pilates, aerobics classes and just the plain old gym. Pretty much any physical activity should have some positive effect. What works best for you depends on what you need to do - lose weight, tone up, etc., and also varies a lot by person. The instructor and her/ his knowledge of postnatal needs can also impact. If you need to shed pounds try something that will get your heart rate up (brisk walking, cycling or stationary cycling, eliptical machine at gym, etc.) are good starters that aren't too hard on the abs. If you need to tone up yoga or pilates can help. There are all sorts of different types of yoga and pilates also - some classes are much more aerobic while others have more of a stretching approach. If you need recommendations for pilates instructors send me a message and I can provide who I've used via PM. If you are already comfortable with basic yoga postures or mat pilates a postnatal DVD can be useful for at home use. Quite a few DVDs on the market have short workouts for new moms.
4. LLL can provide great advice on improving quantity of milk - the basics are on their web site and you can contact them for more info.
5. There are creams (Strivectin is one brand) that can have a lightening effect and laser treatments for more intense treatment (effectiveness depends on your particular marks and skin type and the skill of the dermatologist applying the laser treatment). Coco butter is also recommended quite a bit and is a good, inexpensive start.
Best of luck and congrats on the baby
