In this tutorial you will learn a very simple thing that will give your images top quality and very low sizes.
Select the image your want to save, for me its going to be this little piece.

now go to File-/ Save for web.
Now use these settings...

Just for Specifics heres what the settings are...
JPEG
Very High
Quality: 80
Blur: 0
Leave everything else unchecked
Now click Save and define were you want to save.
Here are a couple of examples.
Pic saved WITHOUT this techniqe

113 KB size.
Here is a pic saves WITH this techniqe

49 KB size.
Hope this helped you all!