Starting a flooring business and want to know what to register as Limited liability company,limited liability partnership,corp or just a General partnership.I'm in Washington state,have a partner(not my spouse) so I can't do sole-proprietorship.

Try this link: Choosing the Structure of Your Business or Organization (http://www.secstate.wa.gov/corps/registration_structures.aspx)
It may also be advisable to talk with an attorney or CPA who can explain the tax benefits and liability issues