Simply put, start taking care of yourself (if you aren't already). Eat right. Work out. Basically, be healthy. You are your baby's home for 40 weeks. You want your baby to have the best home he or she can, so that's your goal.
Also, prenatal vitamins are strongly suggested. Not because bad things will happen if you don't take them, but because they've been proven to have positive effects for babies. The folic acid content in them is perfect for a lady such as yourself, preparing herself to house a little bundle of life.
Also, if you smoke, stop. Reason to stop now, is that if you become pregnant while being a steady smoker, quitting cold turkey will be a shock to your system, the effect of which will feed on to your baby. I've even known a doctor to advise his patient to just cut back gradually rather than stop, to avoid trauma to the system. So if you can quit any 'bad habits' beforehand, you should.