We were having some trouble getting pregnant again after our first baby but we finally managed to conceive again after a year of trying. I made this little website to help other couples in our situation. I know that if we would have done things right from the start it wouldn't have taken a year, so read and learn.
First of all you've got to get your periods regular after postpartum, the way to do this is to just take it easy, don't stress too much. Eat healthy, get some physical exercise, and don't smoke or do drugs. Moderate alcohol consumption won't influence your periods but you should be living extra "clean" for at least three months before you attempt to get pregnant to minimize the risk of birth defects. This means eating healthy, no medications (not even aspirin) unless absolutely necessary, no alcohol, tobacco, or narcotics, and start taking prenatal vitamins already even though you're not pregnant yet.
Second, you need to track your morning temperature and figure out your ovulation dates from this, you can do the calculations manually or you can get a software to does that part for you. Most software out there dealing with this is absolute garbage, there are a few good ones. The most accurate fertility software available is "MommyMaker", please see their website www.mommymaker.com for more info. There are other softwares with nicer interfaces but they're not as accurate at predicting your ovulation date, and that's what's important.
Third, you need to attempt conception at the right time. Some research says that the best time to attempt conception is two days before the ovulation date. But other research says the actual ovulation date is the best time. What we did was to stop all sexual activity 10 days before the ovulation date to save up sperm, and then go at it two days before ovulation, and again one day before and again on the ovulation date.
These are just a few tips, but I hope they help.