when you wash, you want to wash all over your head, and scrub. even wash at your hairline, on the back of your neck, and behind your ears. those are the spots people forget the most. conditioner is optional.
rinse throughly. if you don't, when you come out, your hair won't just be wet, it'll be soapy and gross. and that's what makes your hair dry out. after you rinse, dry your hair out with a towel. make sure it's completely dry. you can also use a blow dryer, which works best.
if those tips don't work, then you can always try using shine shampoo & conditioner, or leave in conditioner for extra shine.