If you're having trouble getting the perfect sized screen shot to help with your explanation, here's a small Windows utility that works pretty well: Cropper
. I personally use SnagIt
, but Cropper works good for a free one. Once you have it installed, the output folder is "...\Documents\Cropper Captures
" (on Windows 7). Or better yet, go into the Options and change the Output Location to your Desktop. Oh, one more setting for Cropper (right-click the tray icon), choosing the PNG output format will be the best for attaching to forum posts.
There are many screen capture programs out there, so do your own Google search if you'd like.
I'll not be much help on the Mac side, but I think that has some decent built-in options.
Post here if you have any other suggestions.