There was a lot that confused me about this new world I was taking baby steps into. How did you upload and how do you know what to do? So, here is a helpful hint that Jenn just shared with me.
I'm writing as if you know Photoshop, so please let me know if I'm skipping ahead for anyone.
The images should be 600 x 600 pixels at 72 dpi. (you can do that in Resize Image)
For some reason, Jenn says you need to Unsharp Mask - I don't visually see a difference, but she claims it must make a difference when its uploaded to the sites. I didn't do it but here are the numbers she gave:
Go to Filer>Sharpen>Unsharp Mask
Radius: around .5
Threshold: around 15
Then Save for Web. Optimize so that the file size is 150 dpi or under.
We did this by noodling with the 'quality' numbers. Mine generally ranged between 71 and 59.
The reason for this is that some (most?) sites only allow uploads of 200 dpi or less. Some much less. Some don't tell you until you've tried to upload and gotten an error, which can be annoying. Save yourself the hassle, do it now.
Then I made a folder with my Projects folder titled: Web resized. I drop them all in there.
I still don't quite know how you get to know what sites/pages/links your challenges were on and how to find them again - if they are multiple day ones, but that is a question for another day. :)