For Nokia 6310i and similar phones

1) Install Nokia PC Suite
2) Find ringtones in RTTTL format and save as .txt
    Make sure you are legally allowed to use the tones
3) Start Nokia PC Composer and connect phone (via cable or IR)
4) Convert track to tone
5) Go to Tools | Update to phone to upload to phone
6) Use Tools | Send Tone to SMS to someone else

Nokia 6310i can have 10 custom tunes
Uses a DLR-3P cable