Conversion varies between the movements in Judaism (Orthodox, Conservative, Reform, Reconstructionist). My conversion was through a synagogue that aligned as Reform but followed a very Conservative service. The synagogue was small and rural and had to accommodate many different movements. Orthodox will say that my conversion is not "valid" because it was not an Orthodox conversion. Some Conservative synagogues would not accept my conversion (this is changing however). One thing my beit din tried to do was make sure that my conversion would be accepted by most.
Halakha means according to the body of Jewish law.
According to Halakha, for a "legal" conversion there are a few requirements that must be met. These requirements must be demonstrated to a beit din before a conversion candidate will receive his/her certificate of conversion.
1. Circumcision (brit milah). Sorry guys, you're gonna have to get cut. If a man has already had a circumcision then he must still go through the hatafat dam brit. A hatafar dam brit is when a drop of blood is drawn from that part of the man's body where the circumcision was already performed. I am glad I am a woman. But I am told it is not as bad as one would imagine it to be.
2. Ritual immersion (mikvah). This applies to all converts. The mikvah is a pool of water meant for ritual immersion for various reasons. The mikvah is where Christians derived the concept of baptism by immersion. For a halakha conversion the convert must immerse in the mikvah, say a blessing and immerse two more times. Every part of the body must be touched by the water of the mikvah. This means, you guessed it, when you immerse in the mikvah you are in your birthday suit. Most mikvahs are very nice and warm and very good about maintaining the modesty of the convert.
3. You understand and accept the responsibility of Torah law.
***Side Note: Orthodox will only accept an Orthodox conversion. Many Conservative synagogues will accept a conversion as long as all of the above (plus meeting with the beit din) were met. Reform will accept any conversion. I am unfamiliar with the policy of the Reconstructionist movement but if I remember correctly they follow along with Reform.***
The beit din is the scariest part of conversion. The beit din is made up of 3 learned Jews (they do not need to be rabbis but there is usually at least 1 who is a rabbi). The beit din is there to determine if you understand what you are undertaking. That you are converting of your own free will and that you demonstrate that you have been learning and studying and will continue to study after conversion. You do not have to be perfect, most beit dins do not expect perfection. There is much to learn before you can even be recommended for a beit din.
So before you even have to worry about that list above, study... study... study.
I studied for conversion for 3 years prior to my conversion. The first year I was studying with my family and following the Noahide Laws (will make a post about this another time). After that year I felt drawn to more. It was at that point that I contacted the rabbi and began attending services at the local shul (synagogue).
Traditionally, when a person comes to the rabbi seaking conversion, the rabbi must deny the person 3 times. This is kind of a "test" to see if the person is truly serious about wanting to convert.
Once I started studying with the rabbi I had several additional tasks required by my rabbi. I had a reading list of books. I had to watch a couple of movies (Oh, the pain! The agony! The TV... Score! I highly recommend "Fiddler on the Roof" and "Keeping up with the Steins" but careful of the 2nd one if you have little children around). I had to keep a journal detailing why I wanted to convert and the changes in myself and my home life during my course of study. I went to lessons with the rabbi where we talked about everything from the Jewish lifecycle to the holidays to topics of interest to me. The bare minimum for conversion was at least 1 full Jewish year, to become accustomed to the different calendar and learn the holidays and rituals.
Once my rabbi thought I was ready, he recommended me to the beit din (as my husband was also converting at the same time, through the same process, with the same rabbi, we had the same beit din - only he had to go through the hatafat dam brit - whew!). We each met with the beit din individually and then together. Once the beit din put their "stamp of approval" on us, we went to the mikvah.
The following Sunday (Sunday only because it was a holiday - Shavuot) we had our first aliyah to the bimah (an honor to be called to the front of the sanctuary) where we each received our Certificate of Conversion.
My family has been living Jewishly for 4 years now and we are always learning more. We are looking forward to Pesach, our oldest is preparing for his Bar Mitzvah (conversion of children is a whole 'nuther topic that I will write about at another time), our daughter just had her consecration and we are enjoying the life that G-d has blessed us with.