If your hair is at all naturally wavy, this is something you could do. When you take a shower, use a very moisturizing conditioner. Then, when you get out of the shower, use some sort of "molding" creme (lots of brands, different names that do the same sort of thing). Even a really good moisturizing/volumizing/mousse will work. Make sure you only use a very little bit when your hair is still WET or else it will look sticky when you are done. Ok, now blow dry your hair so that is less than damp, but not completely dried. If it's poofy, this doesn't really matter right now. Pile your hair on top of your head and twist it around into a tight coil. Put a hair band around it, but not one that is too elastic (or if it is, make sure that it won't leave crinkles). I do this a lot in the morning, leave it like this for about 30 minutes, sometimes longer or shorter depending on time, and my hair will be nice and wavy/curly when I take it down. You really have to be careful what you use to keep your hair up in the coil or you will have marks on your hair when you take it down. I find big clips or cottony headbands twisted around and around work well. If you want to set it for hours you could hairspray it lightly.
And one way to make sure your hair stays healthy is to be cognizant of your hair type and how often you chemically process it. My hair is kind of coarse and so it dries out if I dye it or highlight it too often. If you have really fine/smooth hair, it doesn't seem to be affected as much. I had a friend bleach her every few weeks for years and she never had frizz or split ends, it was always smooth. If I highlight my hair once a year I can tell it's a little bit angry with me even for that =D
