Your Domain name is the first thing that will attract or repel potential customers.
Don't scare people off with a poorly conceived URL spend some time researching exactly what your intended customers are searching for & name your site accordingly.
If you already have an existing business & an established clientele then this part of the process is simple - people looking for your business will search your business name & if that doesn't work they will expand their search by adding city or state.
If your business name URL is available get it - If not then there are a number of techniques you can use.
i.e. If your business name is "Tony's Pizza" & is on Summit Road in Elgin Illinois (No such Pizzeria)
1. Hyphens - Tonys-Pizza.com
2. Emphasis - BigTonysPizza.com
3. Property - TonysPizzaParlor.com
4. Address - TonysElginPizza.com / TonysPizza-Summit.com / TonysIllinoisPizza.com
As you can see there are any number of ways to change a domain name that is already taken, make it your own & have your customers find you on-line.
New On-line Businesses
Imagine you were opening a store in your local shopping mall - Although the name is important all the people visiting the Mall will walk by your store, so even if you called it "Cat Food" & sold "Live Fish" your potential customers would still be exposed to your store.
Not so On-line - If you want customers you need a "Premium Domain Name"
A Premium URL is not one you need to spend $5000 on, its just one that targets motivated buyers & along with your Description makes them click on your link.
I am not going to delve too deeply into keyword research here but there are several key factors to consider
General Search Terms - clothes / food / toys / cars, are all very general search terms - People searching this broadly are not looking for something in particular.
Specific Search Terms - pants / lobster /dolls / mini, These are second level keywords they are still not detailed enough terms to define buyers from browsers
Detailed Keywords - Designer Pants / Fresh Lobster Delivery / American Girl Doll / Mini Cooper S - These people know what they want & are looking to buy.
Buy Keywords - Tommy Hilfiger Pants / Cheap Fresh Lobster Delivery / Buy American Girl Dolls / Used Red Mini Cooper
Detailed & Buy Keywords should be utilized in your URL & sub folders to get motivated buyers into your site.
Spend some time researching your idea, consider the various terms that someone looking to buy your product or service may use.
Remember a Premium Domain Name is one that attracts motivated buyers not browsers.