Script into 2 columns. The narrow left column will be the score column (speaking characters primarily), and the wide right will be dialogue, action and sound. Use a strong hook, Time your script (never go beyond 30s), Understand radio ad convention, SFX stands for sound effects (write in left column in all capitals and underline), Use ANNCR for announcer, Use a double dash or ellipses any time you want a slight pause.