I need to know how to come up with content to a site , i.e. if I'm building a new site the only way to know what information to include in that site is to visit similar sites and find out what they show so that I mimic them. This ain't professional and I need to know how to come up with the appropriate content to my site by myself. I googled ALOT ! and found nothing important. some people might say that this is what information architecture is all about but I've read about IA and it seems to me that it deals with organizing the content not and stuff like navigation and sitemaps without any clue for coming up with content .
Is there any article, book title , course , or anything that teaches how to find out the appropriate content for the site instead of looking at other sites and trying to mimic them ?