Here's a pretty good guide to the URLs and parameters for the common ones:
This website has got a bad reputation, but I've rarely had any issues with them. I think any issues I have had were easily handled with some CSS or some htaccess URL blocking.
Nonetheless, I still use it on all my websites. Simply copy the code into the pages you want or the footer if you are using a platform like WordPress, and the code takes care of the rest.
FYI: I am in no way associated with the owner of that website.. I just think whoever created it did a great job at making social sharing easy... and no plugin required!
On Mobile phones, users tend to go the native way - for most of the people, they use Chrome's share because it's easier.