Flash Tutorial – Reducing SWF file size (How To)
How to reduce swf file sizes: Written by Paul Bainbridge – Innovative Designs
Replace images for vectors wherever you can.
Import images dynamically if vectors is not an option.
Reduce publish settings for images..
Do scripted movement rather than tweens… puts pressure on processor rather than file size to the swf.
You can also simplify your vectors by using the optimise option.
Use symbols for repetitive graphics.
Reduce frame rate and shorten tweens.
Sometimes (depending on the font) you should break apart the font to make it a vector then you’re not importing the font, just drawing a simple shape. This does depend on the font, and how often characters are repeated.
You can opt to use device fonts for body copy.
Make sure PNG’s are close cropped because believe it or not that transparent space actually ways something.
Generate a size report from your publish setting to see where the weight lies in your file.
Delete any stray or inappropriate key frames because this is causing a redraw.
A motion tween can often be heavier than a shape tween… because motion tweens don’t do anything mathematical the compiler actually converts them to individual key frames.
All masks and hit areas can be done with one square transparent symbol that you use throughout your FLA.
Then beyond that its tricks you use to give the illusion of an object but with optimising in mind…
i.e. if you have a symmetrical bitmap, save half of it out from Photoshop then flip it to make the whole graphic.
Similarly flipping graphics to get the opposite action rather than having to different graphics.
If you’ve got any bitmaps that are silver, save them as greyscale.
Make use of tint and other advanced colour setting for symbols rather than recreating graphics.
It’s endless really… but depends on the job.
Paul Bainbridge

A great bit of info there Paul, thanks.