Graphic Design/Principles of Design
Some of the most commonly acknowledged principles of design are alignment, balance, contrast, proximity, repetition, and white space. These are all elements of graphic design "composition." Additionally, compositions are evaluated based on the use of (and the successes or failures of) harmony, emphasis, gestalt, pattern, movement, rhythm, proportion, and unity.
What is Graphic Design? 
Graphic design is the art of visual communication through the use of images, words, and ideas to give information to the viewers. Graphic design can be used for advertising, or just for entertainment intended for the mind.
Alignment in graphic design is the keeping of related objects in line.
Designs in balance have the parts of the design arranged in a planned, coherent visual pattern. "Balance" is a concept based on human perception and the complex nature of the human senses of weight and proportion. Humans can evaluate these visual elements in several situations to find a sense of balance. A design composition does not have to be symmetrical or linear to be considered balanced. It is also true that perfectly symmetrical and linear compositions are not necessarily balanced. Asymmetrical or radial distributions of text and graphic elements can achieve balance in a composition.
Distinguishing by comparing/creating differences. Some ways of creating contrast among elements in the design include using contrasting colors, sizes, shapes, locations, or relationships. For text, contrast is achieved by mixing serif and sans-serif on the page, by using very different type styles, or by using type in surprising or unusual ways. Another way to describe contrast, is to say "a small object next to a large object will look smaller". As contrast in size diminishes, monotony is approached.
Making a specific element stand out or draw attention to the eye. Emphasis can be achieved in graphic design by placing elements on the page in positions where the eye is naturally drawn, by using other principles such as contrast, repetition, or movement. Bold and italic type provides emphasis for text. Graphic elements gain emphasis through size, visual weight, color, complexity, uniqueness, placement on the page, and other features.
Sometimes considered a distinct principle of design, gestalt is the concept that "the whole is greater than the sum of its parts." Gestalt is a concept from psychology, where theorists note the propensity of humans to conceptually group things together to make a meaningful whole. When viewing designs, humans apply this principle unconsciously by seeing connections and relationships among and between the elements in the design. The overall perception of gestalt in a design is created through harmony, unity, balance, proportion, proximity, and other visual cues. Designers can use this principle to create visual connections and relationships that clarify and strengthen the overall "feel" and meaning of the design.
As with music, graphical elements can be said to be working in harmony - the individual parts come together as visually compelling and a meaningful whole. Disharmony can also be used just as it is in musical compositions: to enhance the emotional complexity, to challenge the viewer, and to give a contrast within the overall composition.
Movement is creating an instability, making motion to blur the image. Movement can be achieved by using graphic elements that direct the eye in a certain direction such as arrows that point the way overtly or a series of lines or dots that get progressively larger or smaller, creating a more subtle sense of movement. Movement can be accomplished simply by using a photograph or clip art of something moving - a runner - as opposed to something stationary - a person standing.
This indicates the relative visual size and weight of particular graphical elements in a design composition.
Closeness or distance of individual design elements. Close proximity indicates a connection.
Repeating a sequence; having it occur more than a few times. In design, repetition creates visual consistency in page designs, such as using the same style of headlines, the same style of initial capitals, or repeating the same basic layout from one page to another.
Excessive repetition (monotony) may lead to boredom and uninteresting compositions. If one cannot avoid excessive repetitions for any reason, do not forget to add some visual breaks and white spaces where eyes can rest for a while.
Successful designs have an effective ebb and flow. Text and graphics should seem to be paced and patterned. Spacing is an effective application of this principle. Second, human beings are more comfortable with variation in general. Psychologically, most any serious lack in variation of anything (a solid, a line, a sound, a situation) can become very boring. Adding a little variation at non-specific intervals (every now and again) gives most any design an interesting appeal as long as it is not overdone.
In setting type, rhythm can be created or disrupted. Compare the gibberish strings, "as erav mono ewone zenao oro remuna oravanam" and "githol urtym reislyt quadirit". Notice how the latter seems to be more organic and readable than the former. This is resultant of two things. One, the eye more easily follows abnormalities and variation, like an ocular foothold. Too-narrow columns result in over-hyphenation. Images that interrupt a passage of text can break the rhythm for the reader and they could disturb the visual appearance of the page.
Unity creates a feeling of wholeness. Unity is usually achieved when the parts complement each other in a way where they have something in common. Unity can be achieved by use of the same color, or different tints of it, or using a similar graphic style for illustrations.
White Space 
Areas of a design devoid of text or graphics. White space includes margins, gutters, space between lines of type (leading), off-set of text from images (text wraps) and any other part of the page that is empty. White space is also analogous to "negative space" where "positive space" is defined as images, blocks of text, and other graphical elements. In graphic design, the white space, or negative space, is considered an important element of the overall design. It is used - and evaluated - based on the same criteria as the rest of the elements in the design. White space can add to or detract from the balance, unity, harmony, rhythm, and overall success of a design. White space can give emphasis, contrast, and movement. It can be used for repetition and pattern, and work within various relationships with other elements of the positive and negative spaces in the design.