Your grumpy Mod from Germany speaking here …
Frequently posters fail to add pics in their posts, so, a few remarks from the janitor:
pic/file size is restricted - for various reasons.
Unfortunately, well known screen-grab shortcut cmd-shift-3 creates full-screen png - nice & detailed, but huge. Too huge.
=> before uploading, use Preview.app to resize&reformat, suggestion: max 1200pix wide (or long) and as jpg.
Cmd-shift-4 allows to drag open a selection rectangle… less is more!
To attach a pic, use the Attach button in the Post Editor.
To insert a pic in your text, you have to Attach it first, then hit Insert
• Does it need a pic? This pic?
Sometimes, a pic tells more than a 1k words, sometimes it lefts the watcher clueless. Mentioned Preview.app has an impressive toolset of circles, arrows, a loupe, colors etc to direct attention. I’m talking to movie-makers, hey, you should know!
• Does it illustrate the problem/post?
A full-size screen-grab of your About-this-Mac doesn’t add any info you couldn’t write in half a line of text. When you discuss a before/after prob, it should be two pics, shouldn' it? Trouble with Inspector settings should show … you got the idea.
• No full-quotes! Please. Just for me.
… ok, there’s no board-rule telling this, just personal preference, sort of politeness … esp. a mile-long full-quote with dozen of pics and an added “yeah, right on” or like makes me arghgh.-
• Ext. Storage
Some prefer to attach a link to some external service … be kind to us, use services which don’t make my Mac going rogue popping up all sorts of ads and ‘polls’ ask membership or whatever.
• Links to pics
Check your link. Which leads to: …
• Check your post after posting it
When I don’t see a pic in your post, you don’t do either. Edit it. No ‘fire and forget’, please.
… this post is beyond 140characters and includes no pics - hmmm? Not so smart.
I'd like to tell what I do when posting screen shots. Open in Preview, 1st thing, Tools > Resize, set width to 1200 (height is going to be whatever). Then Export to a JPEG, 80% quality. That pretty much always works here.
Bear in mind the Mac, and depending on the monitor it is using, can do screen shots at 144dpi, and at a full screen size (in pixels) that makes for a very needlessly HUGE image.
Yeah, your Mac is powerful, but the internet is not that powerful...
In addition to what Ben said, you can also use Preview to do this on multiple images at once. E.g, import 10 images to Preview, resize all of them to 640 x 480, export them at medium JPG quality. No, do not post 10 images on this forum, but if you email in-line images to someone else they will thank you for this: