there are many websites out there dealing with this issue, try searching on Google. The main wires are the loop (for power), Earth and neutral. You should look at another ceiling rose and follow it's connections
Darren, April 2006
Depends on how your lighting circuit was designed. Try getting a DIY book with lighting circuits in it. Finally if you arre installing a new rose, from 2005 it became illegal in the UK to carry out certain electrical work unless you are a "compentent person" or have it inspected after the work.