MicroSort®:
The MicroSort® process sorts sperm by male and female by a process that measures differences in the DNA. Then using an intrauterine insemination (IUI) or in vitro fertilization (IVF) the enriched sample of sperm is used to help you conceive. About 92% of those attempting for a girl do conceive a girl, while the success rates for sex selection and boys using MicroSort® is lower at 81%. The pregnancy rate for using an IUI cycle is 15.6% and the overall IVF/ICSI clinical pregnancy rate is 32%.
Preimplantation Genetic Diagnosis (PGD):
This is the most effective technique in sex selection. With nearly 100% accuracy and the ability to select not only sex but a healthy embryo makes it very popular. Though this is a costly and intensive method of sex selection that uses in vitro fertilization and does biopsies on the embryos before they are returned to the uterus.
Shettles Method:
The Shettles Method is based on the fact that male and female sperm travel and survive in the reproductive tract for varying amounts of time. So you time intercourse about 12 hours prior to ovulation for a boy and several days before ovulation for a girl. This is a very simplified explanation of Shettles.
Ericsson Albumin Method:
With Ericsson, the sperm is filtered through albumin and then an intrauterine insemination (IUI) is done with the sample. While the sample doesn't provide you with more of one particular sex, like a MicroSort® sample, it does help select the sex of the baby. For a girl, Clomid® is used since it has been shown to increase the number of girls.
Other Methods of Sex Selection:
There are other methods of sex selection, including prepregnancy diets to alter the pH balance of your body, timing methods that differ from the Shettles Method, O+12, supplements, and positioning. These low tech methods are not as accurate as MicroSort® and PGD and are sometimes dangerous.
Source: pregnancy.about.com