1-Make a list of companies or brands that sell fashion. Also write what type of fashion each company makes. These are called "fashion categories". Some examples of categories are: footwear, accessories, junior wear, and career wear. Decide what category interests you the most.
2-Start a style file or portfolio with pictures of that type of fashion. If you want to add sketches, that will only add to your notebook. Make a list of companies or brands in that category, as well as your favorite and most inspirational designers.
3-Keep fashion inspiration. Buy a simple cork board and paste, pin, and tack inspirational fashion pictures on it. Put it up somewhere where you will constantly see it, like your bedroom or a 'studio room' if you have one. Buy some folders and file fashion magazine clippings or computer print outs in it. Subscribe to fashion magazines like Vogue or Teen Vogue and stay on top of the latest trends. Keep a little book of fashion cuttings in your bag or purse. If you're constantly surrounded by fashion inspiration, the ideas will come flooding in. But remember - don't ever copy a fashion piece. Just be inspired to create your own.
4-Take an art class in drawing and sketching. Learn to draw drapery, to understand the flow of fabric (how it drapes). You'll start to notice the dark areas in the folds, and the lighter highlighted areas. If you can find a class that draws people or "life drawing", take that too. If you can't draw real people, start drawing from photos. Use tracing paper to trace over the pictures of fashion models. Then slim then even more and elongate them for dramatic effect. Also learn about color, and mixing color. Know what colors look good together and how color groups are assembled. Focus on drawing actual fashions, and perfecting drawing bodies.
5-Get a mannequin that you can pin fabric on, or drape to make designs to see how they would fit a body. Draping is another word for covering, dressing, or hanging cloth in loose folds. You can learn about this in a sewing class, or through a fashion school or program. Also, if you want to enter a fashion design college but you aren't the greatest at making sketches to add to your portfolio, it's always acceptable to just pin clothing you have designed and sewed onto your mannequin and take pictures of it.
6-Learn to sew clothes. Take a sewing or dressmaking class. Study the patterns and become familiar with sewing pattern shapes. Sew for real people (like family and friends) so that you get familiar with body shapes and fit. Also learn about fabric. Know what fabrics are made from (silk? wool? cotton?) and how they are woven (velvet, twill, satin). Know which types of fabrics are best for each of your designs (stiff fabric, drapey fabric, sheer fabric, etc).
7-Make clothes for other people. You will learn a great deal about dealing with a customer and fitting the human body in all its variations (tall, short, petite or large). You can also charge money for your work.
8-Learn about fashion trends. Visit web sites such as pantone.com to see what colors are going to be in fashion. Also try to predict what fashion will be popular in the future. Check out sites like elle.com or style.com
9-Learn how fashion is sold. Is it being sold in stores or online? What are the major department stores? What stores sell the category of fashion you are interested in? Also learn about "targeting your customer base." This means knowing the type of person who will buy your fashions.