Advice on choosing good search terms
Choosing good search terms are the key to a successful campaign. You need to put yourself in the shoes of one of your potential customers and envisage how they will find you on the internet. So for example if you run a car dealership that sells Ford cars, you might want to use "Ford Escorts" as a search term.

You may not even want to receive enquiries from outside the UK, so you might qualify the search term by adding a geographically specific element eg.
"Ford Escorts London".

Precision is the key, because the more vague the term the less qualified the lead, eg. If you made your search term just "escorts" you would not only receive enquiries from people wanting to buy a car, but also people wanting some company for the evening!

Similarly if you just made the search term "cars" then you would get enquiries from people wanting all types of cars which is no good if you only sell Fords.