My favorite book on Word is Microsoft Word 2010 Bible by Herb Tyson.

Lynda.com has a good video tutorial on forms.

Check Greg Maxey's site. He has wonderful resources for forms (legacy and content controls). Microsoft Word Help, Tips and Tutorials @ The Anchorage Certainly download his legacy form controls Add-In Add Classic FormField Controls to Ribbon if you are going to be using legacy formfields. The lock button alone is worth the download.

I have a page I started on forms. The links in it are useful but the page is unfinished.
Making Forms with Microsoft Word Especially look at the links to Dian Chapman's acticles. These do not cover the new content controls but are a good discussion of how to build forms in Word.

Avoid ActiveX controls until you need them, they require programming and won't work for you unless macros are enabled.