Taking that first step can be very hard. There are stories of gals who always looked like gals, but most of us looked like guys in the beginning. At some point I think most of us just said "screw it" and went ahead.
Appearances and voice are important. You can ease into it with an androgynous look. You can begin wearing women's clothes that don't look a lot different from men's but are cut differently. I started in jeans and turtlenecks. (It gets cold here.) It was weeks before I ventured out in a skirt or heels. I still rarely wear any really girly tops – they just aren't my style.
I believe that hair and makeup go a long way. It can be the subtle things that make a difference. Get a woman's haircut. (Women's hair is cut differently than men's – more on a bias than blocky.) It makes a big difference. A little makeup lightly applied will be more effective than heavy makeup. You want to look like a natural woman. If you can't find a friend to teach you, go to the makeup counter of a department store and ask the woman to do you over. If she won't do it, go to another.
But manner, carriage, and attitude are very important, too. If you walk like a man and carry yourself like a man, people will think you are a man. If you act like a man, people will assume you are one. And so forth.
And take heart – we've all gone through this and managed somehow. Some of us have an easier time than others, but it is difficult in the beginning. You are asking to be accepted as your true self – something you've never done before. The difficulties make us strong.
Good luck, sweetie. You'll get there when you're ready.
*hugs*
Kate