Paint is still my preferred way to save screenshots. Press the Print Screen button, paste into Paint, draw a red line, save.
So here's a pretty cool thing using ShareX:
http://i.imgur.com/5WEnr6b.png
Ok so it's another screenshot tool. Capture all, a window, a selection, etc. Bind global hotkeys.
But where it really shines is the easily configurable "after capture" and "after upload" toggles. In the screenshot you can see I have: copy to clipboard, save, and perform actions turned on. The first is nice because I can easily paste into Slack. The middle is nice because it goes to a particular directory and I have history. But the latter is something I just turned on to show you how it can easily open the screenshot into mspaint.exe for you.