Anti-Hotlinking in plain English, please?

[Pagan]

I will admit this is one area I need a better guide to. When I have tried this or that technique in the past, I shot myself in the foot and was unable to see any images on my domain. I can't get by on just mimicking what I see others doing - I need to really understand this area as I have now been hit by the third round of hotlinking. I have used anti-hotlinking functions available through the control panels on two of the three hosts, but obviously there is a work around and/OR I didn't do it right for my needs.

Let's say I have two domains on the same host, under the same account. Let's call them Domain A and Domain B just to be simple and clear. Both domains have freesites and galleries plus blogs. Domain A never shares anything with Domain B except for text links. All graphics and images for the sites on Domain A are housed in subdirectories. Same goes for Domain B. I don't call any images or files from Domain B on sites on Domain A and vice versa.

When I build a freesite, I have a structure similar to this:
Domain A
Freesite or Gallery folder
Individual Site
folder for pics
folder for thumbs
index.html
site pages
folder for mirror 1
folder for mirror 2

Individual Site
folder for pics
folder for thumbs
index.html
site pages
folder for mirror 1
folder for mirror 2

Rinse, lather, repeat

My folders for mirrors only contain the .html pages, and I call the images from one directory level up, so to call an .jpg up from mirror one, it is ../images/pornpic.jpg. I do have a very few sites on my oldest domain that call sponsor banners from a central image folder, but it is all within that domain.

So, if I wanted to write anti-hotlinking for my .htaccess file to block everyone but me from hotlinking within the one domain, what is the best way to do it? What about the handful of link lists that want a tiny preview image - better to put those in a directory and allow access? Does it vary from server to server? What is the most efficient way for page load time and server load? Are there ways for the determined hotlinkers to get around it? I did read through several earlier discussions about .htaccess but am not afraid to admit it didn't really make sense and the sites I have hit on the mainstream side of the house were not much better.

Now be gentle guys, please. I know the logic is there if I can only find the beginning of the thread to follow.

Thanks much!