Hi
To be able to determine this, you must consider the following:
1. Research: search the web for good sites e.g Google Adwords, Pay Per Click
2. In your search, consider their history and achievements. These will give you an update of their success in business and how many traffic they have been able to pull.
3. Target Audience: This will show you whom you are looking for. Whom do you want to reach? Then you check sites who deal with it. It saves you time, energy and cost.
