The first step is to recognize what custom fields you want to use. In this example, let's assume that your blog is a movie review site. You have the following custom fields on your posts.

1) Rating (4 out of 5 stars...)
2) Audience (G, PG, etc)
3) Movie Length

Here is a demo

So i had a client who needed to enter into their site a list of the manufactures that they sell in their store. In the past, i have set up a category called "Manufacturers" and then told them to create a new post for each one. The following client, just wanted the manufacturer name, logo, and website. So i created 1 wordpress page called "manufacturers" and created a custom field on that page called "manufacturer info."