AddThis is my favourite method of adding social media buttons in one hit!
All you have to do is join, and it's free! However it does not work on google sites. All is not lost as good news! The amazing guys at AddThis have provided us with a google sites gadget.
Go to your site, hit edit page and place your cursor where you want your social media buttons.
Click on insert then more gadgets, in the search box type addthis6 and add the gadget (height 32 pixels width 230 pixels).
Fill in your name as the user name, enter your sites url, enter a description and title for your site.
Pick which Social media buttons you want your site sharing on, get your +1 on in the same position as in the pic below ......
Untick Display Title On Gadget and Show Border Around Gadget.
Click on ok and you are done!
Check it out working here! Including +1!