Custom fields, are they like made-to-order crop circles?

Custom fields just give you the ability to define something in a consistent way and call that in a template file so you can do something with it. For instance, I just made a blog for a photographer, and he wanted to sometimes have a related mp3 file available for visitors to listen to alongside a picture he posts. So, I made the template check to see if a post has the custom field "mp3" defined and if it is, the template will automatically display an inline mp3 player that plays the file at the url specified in the custom field. Here's a simpler example. Imagine that you want each post to display your mood when you wrote it if you want to share your mood. So, define a custom field called "mood" as "angry." Then, the template will automatically display "angry" wherever your template calls for the "mood" custom field. For another post, it might display "happy" if that's what you've defined it as.

2nding that custom fields are not really going to help with your generic search results. Usually these things are used with PHP conditional statements to load different designs or enable extra functionality. Magazine-style themes use tags/categories/fields to display featured posts more prominently than others, for instance. Or one could attach polls to the ends of certain posts with a custom field. They are hooks which provide for design and usability customization. You can use them to give certain pages or posts very snazzy layouts or extra features, but they won't effect the strength of the original content as seen by a search engine. (Unless you're using them to pull in related/auxiliary content which is really way beyond the scope of what tags/categories/fields do.)

I have a booklog, called boeklog, and use the custom fields: a] for showing the name of the reviewed author, either before or after the name of the book, depending on what the layout demands. On the single page the author's name above the title looks better, in the title index the author's name below the book title does. b] for showing a picture of the book, next to the first lines of the review, when a visitor either searches for something, or looks in the archives, and categories. Tags are used to get an alphabetical authors list, and also to group reviews that can't be grouped by placing those books in the same, too broadly defined, category. Most reviews have a section underneath them with links to related reviews, for which the tags are used for collecting the data, and a custom field with the author's name is used for extra information.

A lot of the Wordpress sites I've done have been for "websites", rather than blogs, and I've used Custom Fields to aid in that. For example I'll have a "Parts" field that lists all the parts available for a product, and a "TechSpecs" field for all the tech specs - then I can use those fields when outputting the product page. As for tags - you might want to look into custom taxonomies. Take a look at this article, for a good brief on how they work, and maybe some ideas will pop in your head on how they'll benefit your sites: http://justintadlock.com/archives/2009/06/04/using-custom-taxonomies-to-create-a-movie-database

Thanks all for your help. This is one of those areas I just have a mental block about. Shownomercy and backwards guitar's explanation broke through the brain fog. Cheers.