As far as we have advanced in technology, we are still unable to select whether we have a boy or a girl. Parents would like to choose the sex of a new baby for many different reasons. Some would like a sibling of the same sex as older children. Others would like a girl after having only boys.
Without using complicated and expensive lab methods, we cannot select the gender of our babies. There are methods that can be used to try for one gender, but they are not completely effective. The methods have to do with differences between the X and Y sperm. Difference in acidity, mobility, and speed can all affect how soon the sperm meets the egg to fertilize it.