1) Keep your industry, your clients/customers, your advertising plan in mind.
2) The more unique & distinctive a name, the higher the chances that the name is legally available for use. And the higher the chances of obtaining the trademark.
3) Think of your business as having a personality. What kind of image do you want your business to portray?
Specific brainstorming tips:
Think about what you want but more importantly, think about what you DON'T want. If you don't want a 3-word name, don't bother with those. If you don't want non-English words, don't bother with those & so on and so forth.
What are the "types" of names you like? Think about words in their simple forms, e.g. adjectives, Latin roots, mythological names, etc. Compile a listing of the types & then seek out resources, such as books or sites, which specialize in those types.