Testing is the fastest way on becoming an expert internet marketer.
Keep testing and monitor which works. Try to outdo your results after every tweak. Concentrate on testing for 1 year and don't be surprised to get 10x increase in conversions.
a few examples:
1. split-test your ads
2. move keywords around to a different group
3. delete non performing keywords and add experimental ones
For landing page
1. Change copy
2. change graphics
3. add involvement instruments (polls, questionaires etc)
For Social Media
1. use appropriate analytics for each network
2. monitor discussions and see if they talk about buying
3. answer all queries regarding your product