Prospective Freemasons should contact their local Masonic lodge or the Grand Lodge of their region to begin the process of joining. The basic requirements for membership include being a freeborn man of good repute and lawful age who believes in a supreme being and is able to himself and his family. The applicant must also be recommended by another member.
The Freemasons do not accept women as members, but there are some separate female-only and mixed-gender organizations that are recognized by them.
Some jurisdictions may word their basic requirements differently or add other provisions, but the basic requirements listed here are universal.
The wording of the basic Masonic requirements dates back hundreds of years and is somewhat antiquated in some cases. The provision about being "freeborn" come from a time where prospective members might be in indentured servitude of some form. "Ability to support one's self and family" also stems from a time where applicants might have attempted to join solely to gain some sort of financial benefit.
The provision about being "well-recommended" means that a current member must vouch for the applicant and they must be approved by other lodge members. The Freemasons specifically forbid atheists but do not require any particular form of spiritual belief. "Lawful age" is 18 in most of the United States, but some jurisdictions may set this at 21.