First, gather all the information you can about the arrest. This includes the name of the suspect, the date and place of the arrest, and the law enforcement agency involved. These facts will be necessary to search for the arrest report itself.
Next, check the website of the law enforcement agency that made the arrest. Many arrest reports are available online. Sometimes an agency's website will detail the proper procedure for obtaining an arrest report. There are several online databases, such as onlinedetective.com, that are also useful for searching public records.
Often, however, reports can be obtained only through special written requests. If the records aren't available online, visit the police station or courthouse where the individual was detained or tried. Many agencies make arrest reports available to an individual in person, sometimes for a small fee. You may be allowed to examine the report, or to make a copy for yourself.
If the arrest record is not available at these locations, ask the attorneys involved in the case to give it to you. Both lawyers for the prosecution and for the defense will have access to the report, as they need it to prepare their case. While they may be legally prohibited from giving you the report, in certain areas, the decision may be left up to their discretion.
If possible, ask the individual who was arrested for a copy of the report. This option may be difficult if the suspect is incarcerated and unable to send mail with any frequency or disinclined to give you the report.