There are many types of contraception. Some are more effective than others. Some are hormonal, some are barrier methods, surgical, etc. The most effective method next to permanent sterilization is the IUD. There are two types of IUD. The Mirena (most popular right now) is an IUD with the hormone levonorgestrel in it. It is a very low dose progestin that is absorbed only in the uterus (very small amounts may be present in the rest of the body). It keeps the uterine lining thin and the cervical mucus really thick so sperm cannot swim past the mucus to fertilize an egg. The thin lining of the uterus could also prevent implantation if a sperm and egg were to meet (although this isn't usually the case), and it prevents heavy menstrual flow if any. About 4 out of 5 women with this IUD do not have periods which is nice for many women. It is very safe even for women who have history of migraine headaches or blood clots (reasons for not using a combination pill). It is 99.9% effective and easily removed when pregnancy is desired. It takes about 5 minutes to place and is best put in about 8-12 weeks postpartum. It is minimally painful-mostly cramping at the time of insertion and otherwise is not usually painful and requires no upkeep so to say. It is good for 5 years.
There is also the copper T IUD which is made of copper and works by creating an environment that sperm cannot survive in (so similar to the Mirena). It is non-hormonal and will not change the regularity or flow of menses. Your body will be doing what it typically does menstruation wise. It is also 99% effective and good for 10 years, and easily removed if pregnancy or another method of contraception is desired.
Both IUD's are safe with breastfeeding-I forgot to mention that:)
There are hormonal methods such as birth control pills which cannot be taken with breastfeeding except for one pill (mini pill progestin only which is about 80% effective). Pills if taken everyday correctly are about 97-98% effective and they will regulate monthly bleeding.
There are progesterone only methods such as implanon which is a rod we place under the skin in the arm. It is good for 3 yrs and is about 99% effective. It is good for breastfeeders or for young girls that want complete protection from pregnancy, but are not good candidates for IUDs due to multiple partners or never having a child. It will not help with period regulation though. People on implanon do complain about irregular bleeding. The Depo shot is like this, but you come in every 12 weeks for a shot. It has the same side effects as implanon and the same effectiveness. Some people complain about weight gain and acne with Depo, however.
There are also female and male condoms that are in the range of 85% effective if used correctly. I'm guessing my readers know how those work:) They are safe with breastfeeding and don't interfere hormonally with your body, although intercouse can't be as sporadic-you have to plan a little more with this method.
There are more permanent options too such as tubal ligation or vasectomy. I usually don't recommend unless you are over age 35 and know that no matter what life deals you, you would not ever have another baby. Although these procedures can be reversed, it does not always work and is very, very costly! You are better off just doing an IUD which is as effective and easily reversed. Surgery is good however for some people that it would be way too dangerous for them to have another baby or they are older and really know that they would not want another child!