Know your audience:
The most important thing in this medium is the audience. You must know in which time slot this ad will be on air and what type of people listen radio at that time.
For instance, a makeup product commercial will yield best results if it is on air during the day. The reason is that most of the females listen radio at that time.
Know your product:
You must know the strengths and weaknesses of your product. Before writing an ad, you should ask the client to provide you few samples of the product. Use that product and make a list of its positive and negative effects. You are supposed to give maximum information about the product in minimum time. It is not possible unless you know your product.
Formulate your idea:
Now it’s time to work on the idea of the advertisement. Create a story and discuss it with your client or colleagues. Make sure that the idea is relevant and covering all aspects properly.
After finalising the idea, you should start writing script of the commercial. You must know how many sentences can be broadcasted in how much time. Mostly one page is equal to one minute but it depends on lot of things. Formulate more than one script and ask others for a neutral opinion. You must not be rigid rather accept the criticism and make amends.
Make final draft:
If you are satisfied with the idea and the script then make a final draft. Make sure your commercial is establishing the product name and company’s name. You may use names twice in a 15-second ad, thrice for a half-minute commercial and four times in one-minute ad.
Read it loud:
In the end, read out your script loud while having a stop watch in hand. This will give you an idea about its impact and duration.