Double Exposure: to combine 2 different images to make one
Emphasis: to make one part of the piece stand out
Black & White/ Sepia: to find a different tone of the piece and find stronger emotion
Silhouette: a solid figure/ color surrounded by a brighter source 
Boat n' Hand: an illusion in clever perspective; fooling the eye
Rule of 3rds: good photo composition and making the picture unique rather than just in the middle