My daughter has very curly hair, and we have found that using a leave in conditioner is best for defining the curls. There's a great book which we found to give us lots of ideas, called Curly Girl which you might find helpful
I dont have curly hair but my neice does and when she wants to wear it srtaight she uses a straighter they are inexpensive and it only takes minutes to do according how long your hair is,,,than if u have to wear ur hair in a pony tail this will work too also a head band in a pretty stylishis color would look good,,,good luck to u ,, the straighter is the best really looks good,,,