I can never get the right size for attached pics. What size fits into the regular screen without having to scroll to see it all??

400-600kb is good

i usually go on based by pixel size, try not to go over 800 per side.

If you have MS Explorer you may click on ANY picture and select send to "mail recipient" which will then ask you to select a size ......... pick "medium" and the pictures will be sized correctly in the attachment area of mail. Control A on any attachment will be will select all pictures which can then be copied and pasted into this site

1024 pixels wide is a good number for images here.

And anything over 96dpi is a complete waste, so make sure you sample down your 4k images before posting them here.

I just hit 800X600 pixels and save to my desktop, makes it simple to find.
About once a month I dump the pics on my desktop into a folder.