Preventions and cures

According to http://microbiology.suite101.com/article.cfm/sti_and_std, the main ways to prevent STDs are Abstaining from sexual intercourse unless it is with a long-term monogamous relationship; Consistent, correct usage of latex condoms during sexual intercourse. You can also go for annual STD, such as chlamydia, testing which does not cure STDs, but give you an idea of whether you are infected so you can receive early treatment.
The first prevention need not be further explained. So I'll move on to the second. How do condoms work? A condom is a sheath made from latex, polyurethane, or lamb intestines which is designed to cover the penis, creating a barrier between sexual partners and thus preventing the exchange of bodily fluids, which include STDs and semen, between two sexual partners. This prevents partners to be infected with STDs and prevents the female from getting pregnant. Many condoms also include spermicide, to ensure that any semen which may escape will perish before it reaches an egg. Some companies also manufacture insertable female condoms that can be worn by female sexual partners. To use a condom properly, it must be put on in the beginning stages of sexual intercourse, because pre-ejaculate can still infect a partner or cause pregnancy. Roll the condom all the way down the shaft of the penis, adding lubricant to the outside if necessary. Make sure to use a water based, latex friendly lubricant. After ejaculation, the condom should be disposed of properly. In addition to using condoms correctly for maximum efficiency, it is also important to never use expired condoms. Ultimately, if used consistently, condoms shouldn't break and is 97% of the time effective.
So let me move on to the informative, rather than preventive measure, that on tests for STDs. Well, these tests are usually done as a blood, urine, cell or visual examination and there are different procedures for each infection. Some prominent ones include the HIV antibody test which involves a blood sample where doctors check for HIV antibodies. Sometimes, there will be a cervical swab (like a pap smear) like in Chlamydia and Trichomoniasis where doctors examine under the microscope for traces of the parasite or bacteria. Some tests like the one for Syphilis may even require collection of spinal fluid.
Done with prevention, let me move on to cures for STDs. Well, most STDs are relatively easy to cure. In fact, there have even been vaccines created like the one for HPV (genital warts). In most cases antibiotics can cure bacterial STDs. For example, to cure syphilis, a single intramuscular injection of penicillin, an antibiotic, is usually effective if the person has had syphilis for less than a year. Antibiotics are not, however, effective in fighting viral infections such as herpes and HIV. Instead, these viruses can be treated. For instance, HIV can be treated through the use of antiretroviral drugs. For Herpes, drugs, like acyclovir, work to hasten the healing of herpes sores and can also work to suppress an outbreak. However, the above drugs for viruses cannot prevent transmission and are not cures.
Thus the best way to protect oneself would still be protected sex or abstinence in general.
I thank http://www.epigee.org/health/std_testing.html and http://chirkut.blog.co.in/2008/06/23/how-do-condoms-work/ for the info.