I noticed in my webmaster tools that less than half of my URL's are indexed in Google despite most of the pages being fairly established. Is there a secret to get a higher percentage of pages spidered?
create a sitemap of your website and submit it to google webmasters tools. google webmasters link:http://www.google.com/webmasters/ the sitemap depends on your website, if you use joomla for example, you can download a joomla sitemap component.
Sitemap submitted in webmaster tools html sitemap on site good navigation that means the bot can follow links to all pages
Does that have to be done whenever major changes are made - because it has been sumbitted more than a few times. Thanks
You probably just don't have a high enough PR on your homepage. If your homepage has a low PR and low backlink count Google won't think it's important to index your entire site. Which is why some pages are missing. Also you might want to check for duplicate URL pointing to the same content on your site. You can use the conical meta tag to fix that.
Depends on how many pages you have. If you have thousands it might be very difficult to do. Usually if you get visitors on those pages the pages will get indexed on their own. However, if nobody visits that content then you might be out of luck.
Be sure you have a sitemap.xml submitted. And resubmit it every time you add a new page. And another strategy that I use to get new pages indexed is this: Each time I add a new page, I post a link to it under the "Recent..." section of my home page. I keep it there until it is indexed. If you're interested in how to set up such a "Recent..." section, check about 2/3 of the way down signature link #2 below.
There are different ways in getting pages index in Google. Anyway check this one out and hope it can help you in getting your page index http://archive.webpronews.com/2008/0122.html
You only have to submit the sitemap atleast once - and then if and when you are doing any addition or deletion of pages you should take care to update the sitemap also with the new pages (and deleting the removed pages also)