The second step is to choose a period in design history from which you are going to take your styling influences when redecorating your period property.
Your home has lived through several periods in history when fashions and aesthetics have changed the architecture and decoration of houses. There is no rule that you have to choose the period when your house was new. The house may have been extended in different centuries. The first occupants will have brought in older furniture and perhaps preferred older and less contemporary styles.
Based on your choice of styling objective, set a date range over which to explore the prevalent styles.
For example, if you are aiming for museum standard or original period research the history of your home. When was it built? Is it typical of the period, avant-garde or rather retro for its time? If the house has evolved, with extensions and re-working, what is the dominant period? Older houses, such as those from the mediaeval period, are most likely to have been re-worked; perhaps a timber-framed building from 1550 was given a brick skin in the 18th century, and then an extension added in the Victorian era.
If you opt for a selected period, an approach sympathetic to the period of the house, or if you mix the periods, again choose the period to research.
If you want your house to be totally or 'stripped' modern, you can move on to prepare your design, drawing from modern ideas.
Otherwise, the next step is to understand the period you have chosen and pick out the design styles current at the time and what their main features were.