There are varying degrees of feminisation and often the role of a Mistress (or a Master) in this is to guide the person along the path.

The ultiimate goal is to live openly and publically as a woman, not necessarily to 'go the whole hog' and have operations but to be able to do the thing that all wannabe transexuals do for at least a year before the op and live 24/7 as a woman. However, there are many steps to get there.

There is an excellent essay on the subject in the FemDomme society webpage. If you join it as a sub and start 'sissy university' you will find it.

An early step is wearing of female clothes under your own clothes - panties, maybe a bra. You wear these for the day - while at work, while out in the evening and so on.

You need to learn how to do make up, how to dress well for your body shape. So, a Dom/me may give you lessons in this or ask you to try to learn. Wearing full female clothes while in the house in private is another step you may take which will help you practise this. Another step may be to take photos of yourself dressed which may be seen by others or to work up to being dressed 'in public' but not 'completely public' - i.e. at a private party of kink aware friends or travelling to a fetish club dressed as a man and changing when you get there.

You also need to work on things like housework - any Mistress who has a sissy slut will more than likely want her to be able to keep her house clean

In general, a sissy male is 'more female than female' in attitude. By this I mean that where a real woman in the modern day might wear jeans and can do things that 50 years ago would have been considered 'unfeminine' a sissy male generally conforms to the pre feminist ideals of femininity.