Typically, bail bondsmen charge a fee of 10 to 15 percent of the total amount of the bail. In most cases, bail bonds are especially useful when the accused or family members cannot afford to pay for bail. Typically, a bail bondsman must go through bail bondsman training.
Because bail bondsmen are liable for the bail bond amount and the police cannot always find the accused, some bail bondsmen hire bounty hunters to track down people who skip bail. As bail bondsman have a dangerous job, at least financially, it is important that before getting into the profession, one undergo substantial bail bondsman training.
The Judiciary Act of 1789 stated that all noncapital offenses were bailable, and as such, as long as you are not in jail for a capital offense or you are in a state in which the death penalty is not an option, you are eligible to be bailed out of jail. However, most defendants cannot post their own bail, and in those cases a bail bonds agent comes into play. Good references here.