This is American and to do with sports betting as opposed to horse racing, but is interesting and does give an insight to the workings of making an odds line.

http://sportsgambling.about.com/od/...line_making.htm

The impression I get is that the job of odds compiler is pretty high profile and that probably the average track or shop bookie does not know how, or have the time to do it.

Asking an odds compiler 'How do I compile odds' is a bit like asking a car mechanic 'How do I mend my car'. We can all have a go but it takes years of practice to learn all those special little tips & tricks.