1 - if you use [Alt]-[PrtSc] you will only grab the active window. May save you space

2 - the really quick way to Paint is to hit [Windows]+R together, and type "mspaint" in the "Run command" window that pops up.
3 - before you do Ctrl-V to paste the Window, go to "Image- Attributes" in MS Paint and set the image to something small (I use 10 x 10 pixels myself). MS Paint will automatically scale it up to match whatever you past - saves you trimming..
4 - After you paste, press [Esc] so it's no longer marked. That allows you to draw on it, or cut out the bit you want (mark the block, type [Ctrl]-C, then [Ctrl]-N for "New" - say "No" as you just want to keep that cutout, then [Ctrl]-V for Paste)
5 - Save as JPG ("File - Save as - filetype"). Saving it as a .bmp is hardly ever required and it is an incredibly wasteful format for most things..
Just my two cents
