Remember that when users search for your products, they search in a variety of ways.
If you're selling hats, it's important to think about more than just the generic "hats", "cheap hats" keywords, which will also be highly competetive. Think about:
- types of hats ("bowler", "beret", "beanie", etc.),
- brands of hats ("nike", "burberry", etc.),
- Occasions when hats may be worn ("wedding hat", "prom hat", etc.),
- colours and fabric of hats ("red hat", "black hat", "wool hat", "felt hat"),
- and -of course- combinations of the above.
Although traffic for these longtail keywords is likely to be low, it is likely to be higher converting, and CPCs could be less competitive.