N.Y. CVP. LAW § 308 : NY Code - Section 308: Personal service upon a natural person

Personal service upon
  a natural person shall be made by any of the following methods:
    1. by delivering the summons within the state  to  the  person  to  be
  served; or
    2.  by delivering the summons within the state to a person of suitable
  age and discretion at the actual place of business,  dwelling  place  or
  usual  place  of  abode of the person to be served and by either mailing
  the summons to the person  to  be  served  at  his  or  her  last  known
  residence or by mailing the summons by first class mail to the person to
  be  served at his or her actual place of business in an envelope bearing
  the legend "personal and confidential" and not indicating on the outside
  thereof, by return address or otherwise, that the communication is  from
  an  attorney or concerns an action against the person to be served, such
  delivery and mailing to be effected within twenty days  of  each  other;
  proof  of  such  service  shall  be  filed  with  the clerk of the court
  designated in the summons within twenty days of either such delivery  or
  mailing, whichever is effected later; service shall be complete ten days
  after  such  filing;  proof  of  service  shall  identify such person of
  suitable age and discretion and  state  the  date,  time  and  place  of
  service,  except  in  matrimonial actions where service hereunder may be
  made pursuant to an order made in  accordance  with  the  provisions  of
  subdivision  a  of  section  two  hundred  thirty-two  of  the  domestic
  relations law; or
    3. by delivering the summons within the state to the agent for service
  of the person to be served as  designated  under  rule  318,  except  in
  matrimonial  actions  where service hereunder may be made pursuant to an
  order made in accordance with the provisions of subdivision a of section
  two hundred thirty-two of the domestic relations law;
    4. where service under paragraphs one and two cannot be made with  due
  diligence,  by  affixing  the  summons  to the door of either the actual
  place of business, dwelling place or usual place  of  abode  within  the
  state  of  the  person to be served and by either mailing the summons to
  such person at his or her last known residence or by mailing the summons
  by first class mail to the person to be served  at  his  or  her  actual
  place  of  business  in  an  envelope  bearing  the legend "personal and
  confidential" and not indicating  on  the  outside  thereof,  by  return
  address  or  otherwise,  that  the  communication is from an attorney or
  concerns an action against the person to be served,  such  affixing  and
  mailing  to  be effected within twenty days of each other; proof of such
  service shall be filed with the clerk of the  court  designated  in  the
  summons within twenty days of either such affixing or mailing, whichever
  is effected later; service shall be complete ten days after such filing,
  except  in  matrimonial  actions  where  service  hereunder  may be made
  pursuant  to  an  order  made  in  accordance  with  the  provisions  of
  subdivision  a  of  section  two  hundred  thirty-two  of  the  domestic
  relations law;
    5. in such manner as the court, upon motion without  notice,  directs,
  if  service  is impracticable under paragraphs one, two and four of this
  section.
    6. For purposes of this section,  "actual  place  of  business"  shall
  include any location that the defendant, through regular solicitation or
  advertisement, has held out as its place of business.