Pin-up girls are hot. So trying a pin-up hairstyle is always a good idea.
The easiest one is a scarf-tied up do. It's also perfect for a bad hair day, or if you haven't needed to use the "I need to wash my hair" bad date excuse lately and aren't looking your cleanest. Spray a volume booster onto damp hair and pull into a ponytail at the crown. Apply some gel sparingly and use a medium barrel iron to create some curls. Pull your fingers through the curls and randomly pin them into a messy bun. Tie scarf and go.
Another fav is the side pony with teased crown. But don't tease it too much, this is 2014. First flip your head upside down and spray dry shampoo throughout your hair to pump up the volume. Apply extra at the crown and tease with a big comb. Smooth out the tease and add bobby pins to hold the volume. Then tie your hair into a side ponytail behind your ear. This style also gives you the innocent sort of look that will make it so you can get away with anything. Something to keep in mind when you may need to look sweeter than you've been.
For a "I just rolled out of bed and look this good" look, go for the short wavy bob with low side part. Create a low side part and sweep bangs to the side. Then use hot rollers to create soft waves. Don't use too many styling products, any sort of helmet appearance will ruin the effect.
For that date you don't want to ditch, Bridget Bardot-esque waves are amazing. Curl your hair with hot rollers and then use dry shampoo on your roots to give your hair lift.
The rolled back up do takes some balls to pull off, but you can do it. Spritz on some texturing spray to give your hair lift (see a trend here?) Blow it dry to give it volume and then part in the middle. Don't make the part too straight unless you want to look like a bitch (which isn't always a bad thing by the way.) Twist one side back and pin it at the nape of your neck. Repeat on the other side. Pull the ends together and twist up into a soft bun.
Decide what sort of look you want to go for, how much time you have and what type of girl you want to be that day and retro do it.