Unfortunately only about 1/2 of the parents of my students come to parent-teacher conferences. If you can't make the scheduled conference times, call the teacher and ask for a different date/time. Most teachers would be willing to meet before or after school or even have a phone conference. Basically, the parent-teacher conference is a time for you to make sure your child's needs are being met by the teacher and school. If you're unhappy with something that has been going on, send a note asking for the counselor or principal to sit in on the meeting too.
When you come to the conference, see if you can leave younger siblings at home or bring something to occupy them. I've had parents who could barely look at their child's scores because they were busy trying to feed the baby, keep the baby occupied or keep the baby from choking on something in the classroom. Most elementary school classrooms are not going to be babyproof, so letting the toddlers run around is not a good idea. I always provide blocks or baby dolls to play with, but often the little ones are more interested in running around and finding everything in the room that they really shouldn't get into, so sometimes the best thing is for adventurous little ones to stay home.
Be prepared with a list of questions or concerns you might have. Ask your child before hand how things are going at school. This is a great time to bring up any personality conflicts your child may be having with other students too. If your child is struggling, ask the teacher what you can do at hoem to help. Ask if there are any resources that you can borrow from the teacher or school to help out at home.
If there are discipline problems to be discussed, please keep an open mind. I've heard parents excuse their child for almost every behavior imaginable. Also, keep in mind that what might be okay at home is not okay in a classroom with 20+ other students. Ask the teacher about having a behavior plan where your child can earn rewards at home or school for good behavior.
After the conference make sure you congratulate your child on what they are doing well and follow through with any plans for extra help or behavior improvement. And, know that your child's teacher is thankful that you took the time to come see about your child's education!