Doll Optimization

Harddrives and bandwidth both grow in leaps and bounds, but even small files build up after you make 400 of them. There are some things you can do to make sure your dolls are as small as possible.

Convert to PNG format
You can use a batch-utility such as PNGCrush or PNGOUTWin to strip the size down. I haven't done an extensive comparison on the precise formula of PNG vs. GIF differences, but it does scale with file sizes. You will have small advantages on small file sizes and larger ones on large file sizes.
There are three cases where GIF may be preferred: very small (e.g. 50x50 pixels or smaller, 100bytes or smaller) files, animations, or someone is stuck up a log and won't allow you to use PNG (a silly decision, I know!). For the first case I prefer to sacrifice the small difference for the sake of consistancy(that way I know to type .png after all my doll filenames), for the third I prefer to ask questions that make the file-acceptor question their motives, or
Some people like to make the claim that "PNGs don't work in Internet Explorer, and of course everyone uses Internet Explorer!". Here are some facts about this: Internet Explorer 6 and lower will not display the Alpha Transparency that PNG is famous for. It will display the 1-color "GIF-like" transparency that most dollers will be using anyways. Plain and simple. Internet Explorer 7 displays the alpha transparency properly.
Other people have stated that PNGs won't display on their computers. I'm not sure what they're talking about, so if you're one of those people, please send me a screenshot and a list of your computer specs (age, processor, operating system etc):)
Crop your images.
This is the simplest way to save on space and download time for you and your viewers. Basically you make your image just as large as there are pixels colored.
In Photoshop, you can move the marquee after you lay it down, so you don't have to be particularly exact and in PSP, you can select from the highest, rightmost, leftmost and lower pixels to their respective sides and invert the selection and crop like that. Or in either program you can merge all your layers, select the blank pixels then inverse selection and crop. Just remember not to save the PSD or PSP file with the layers merged!
Take an active role in how your color palette is played out.
Most image programs allow you to set a slider percentage of "dithering" (or as some excitable dollers like to refer to it, the "GIF monster") and what kind of color palette you need. If you pixel shade, you probably never have this trouble so long as you tell your program to use 256 colors of the "Optimized Octree" or "Perceptual" or whatever your choice is kind. Toolshaders may be familiar with the loss in quality (unless you use 24-bit png! but then your file size balloons up to about 20kb instead of about 4-8kb, quality over quantity is your call to make). This is where dithering comes into play. Photoshop has a method called "Pattern" dithering, which many novice overuse (I am guilty of this myself, but more in the arena of LJ Icons). Rarely will you have so many colors that you will find it necessary to use 100% dithering. Usually somewhere between 40-60% creates a nice balance between color dispersion and the blending effect. Especially on higher resolution monitors and viewers with worse eyesight 8)

Note about On-line Convertors:

A lot of people choose to use on-line convertors to handle their dolls for them, and I suppose that's their choice. I prefer having a hand in every matter myself. There's nothing wrong with using applications such as Iaza, but I don't plan to unless I find myself in extenuating circumstances:] It transparencizes PNGs fine if you set it to 256 colors, by the way.