This depends entirely on the level at which you want to develop web services at.
At the most basic level, you can simply add some annotations to an EJB or a POJO and deploy it in a container like GlassFish.
At the other end of the complexity spectrum, you may want to customize JAX-WS with your own implementations of Endpoint-s and ServiceDelegate-s...
A good start is having a look at some of the tutorials on the NetBeans web site:
http://www.netbeans.org/kb/trails/java-ee.html Best wishes!
You may also want to find some introductory material to the major technologies and architecture used, like SOAP, WSDL, WS-Security, REST, etc. The http://faq.javaranch.com/java/WebServicesFaq links to many interesting articles and books.