Here are some practical tips to get you started.
Look beyond the diapers and strollers, and take a very serious look at the whole financial picture surrounding an expanding family. You can start with the beginning of course, and look at such things as health insurance and either daycare arrangements or loss of income if you have one stay at home parent. Then, examine your views about paying for your child's education, whether your current accommodation is adequate for a bigger family, and discuss how many children you would like. People raise children very successfully on all kinds of budgets, from the poorest to the richest. Most will do fine in one way or another even if it all happens without any planning. You will go into your parenting adventure with a lot less stress if you and your partner have discussed these issues, and agreed on them.
It goes without saying that having a baby is never a good fix for a bad relationship. We'll mention it anyway because some people do just that. Even if you think you have found the love of your life and you are sure you want to have a baby with your partner and stay with them forever, you may just be wrong. Make sure that you are also willing and capable to raise a child on your own.
While we're on the topic, you may want to talk to your partner about everything you can think of that is wrong with your relationship, and even see a shrink about it. Views on custody in the event you should separate are a good thing to talk about as well. It's not the romantic pillow talk people who want a baby together would prefer, but it is very important.
When it comes to raising a child, there are quite a few different arrangements that work for different families. Both parents can work outside of the home, and can pay for professional childcare in the home, or outside of it in the first few years. There may be relatives, like grandparents, who could take this task on without being paid for it as well. One parent could work outside the home, with the other one being a full-time parent. One or both parents could work from home.
Both parents could work outside of the home part-time, so that one could stay with the child at all times. I am sure there are plenty of other arrangements I haven't thought of. Whatever you do, everything will function much more smoothly if you have planned it all out. These things are most relevant in the first five or so years of a child's life, and far beyond that if you plan to homeschool. Any decisions to take time out of the workforce and be a stay at home parent may have career impact for the rest of your working life, so think about this.
It's the little things that often break a marriage or relationship up. Seriously. Talk about who should do what around the house if you have a baby. Stay at home parents often feel overwhelmed, for instance, while the parent who works outside of the home thinks their partner should take care of all the cleaning, cooking, and accounting. What matters most is that you find a routine that works for you both, and that you can always discuss openly.
Your views on parenting a child are a biggie, the biggest issue you need to discuss with your other half when you decide to try to conceive. It's also the one thing that many couples do not talk about. I've seen no scientific evidence, but I believe hardly any couple discusses how they feel about raising a child before they become parents. They simply believe that their partner, whom they love enough to want a baby with, will agree with them. This isn't always true.
Big parenting issues to discuss for infants include sleeping arrangements (co-sleeping vs crib), breastfeeding vs bottle feeding, circumcision for boys in some cultures, and healthcare. Later on, education, religion, spanking, and grandparent involvement become big topics. You may have your own specific views to add. A good place to start these discussions is to talk about how you were raised and how you feel about it now. Every couple will have different "hills to die on", and every person will change with time. Being able to have open and honest conversations about the past and your visions of the future are a good sign that you will find a way to parent your children that you both agree on.