Game 6 - Had a good position in the start, but blundered it away

This is a game I suppose I should have won had I played idfferently. So I ask you, the reader, to say - what would you have done when white's position was still good to maintain the advantage?

 

Comments and Critiques welcome! 

Hm.. all my games seem to be played as white so far - I've got to play some black games.