It is quite easy to straighten your hair with a blow-dryer. Here's how:
Shampoo your hair as normal, and once rinsed, add conditioner. The conditioner will smooth the hair structure, and protect it from the heat of the hair dryer. Once you have rinsed the conditioner out, comb through with a broad tooth comb, squeeze the excess water gently from your hair, and then leave to air dry for at least half an hour - you want your hair to be dampish and malleable, but not dripping. You can towel dry the hair but be very gentle as you do not want it to tangle and knot it.
Then smooth some hair straightening serum onto your hair, spreading it evenly - there are lots of brands on the market, ranging from inexpensive to premium, use trial and error to find which one works best for you. Then divide your hair into sections and pin the sections out of the way, leaving a single segment. Pull this segment taut away from your head, using a broad tooth comb or a round brush. Apply the hair dryer nozzle quite close to the hair from underneath, and make sure the segment is completely dry before going on to the next one. Always work from close to the head to the ends of the hair, so the hair cuticle segments are smoothed down. Continue to work your way around your head, segment by segment, until all your hair has been dried. Finally, smooth a tiny bit of gloss onto the hair, to hold it and prevent moisture entering back into the hair and introducing a wave.
You can also straighten using a "hair iron" or hair straightener, which is a product that comes with two flat tongs that the hair goes in between. The method for straightening is exactly the same, but you place the segment of hair in the straightener instead of using the blow dryer.
Note that if you straighten your hair too often, you can damage it quite badly. Using conditioner and hair serum can protect it to a certain extent, but over use of heat close to the hair will always hurt it in the end. Once the hair is damaged, it can't really be repaired, despite all the repair products hawked by hairdressers. The only solution to damaged hair is to cut the damaged bits off, and let new hair grow out. You will also need to stop using heat against your hair till the new hair has grown out and this can take months. If you have very curly hair, letting it grow long, which lets gravity straighten it, might be a partial solution that allows you to skip the straightening by heat except for those special occasions.
