If you have longer hair in back and shorter in front, you can add volume to your hair by incorporating some kick-back flicks in a semi shag hair style. If you have long and thin face, then this would be a great option to balance your overall look.
If you have fine hair then adding some subtle wavy texture will enhance your look with more body and volume. Use large or wide barreled iron or even a flat iron to create the random waves and start curling with a distance of 1" from the root. Shake your head after curling to create that tousled look and add hair spray to support. Don't be afraid to experiment and try to have more fun with your hair during week-ends.