There are numerous online services and downloadable apps designed to help you to make your own ringtones, but the steps to creating them are similar. Open the source audio file, select the portion of the file to be used as a ringtone, save your selection in the right format for your phone, and move the result into the appropriate place on your phone.
The first step for making a ringtone is to choose the source audio file, whether by opening it on your phone or uploading it to an online service. Once a file is chosen, select the portion of the audio file to be used as a ringtone. Both online services and apps alike allow you to select start and end points and provide a way to play back the portion chosen to ensure it begins and ends exactly where you want.
Once selected, save the desired portion of the audio in a format the phone recognizes -- M4R for iPhones and MP3 for Android devices. Some ringtone makers allow for the changing of certain variables specific to the format chosen. For example, many allow you to change the bitrate to use when saving an MP3 file. The default values are generally acceptable.
Once saved, place the output file on your phone. Some online services allow you to download the ringtone, receive it via email or push it to directly to your phone. If it is not pushed, put the file in your iTunes Ringtones library for syncing with iPhones or directly to the Ringtones directory for Android devices.