Most films have this kind of information on their technical data sheet (go to www.ilford.com and download some of their film sheets for some of the best examples), but even this is just a starting point, and you can do your own testing for best results.
There are a number of approaches to film testing. I like the method that Ansel Adams describes in his book, The Negative, but you can also just start with the manufacturer's recommended speed and adjust based on your results. Adjusting the EI will change the amount of shadow detail that can be recored on film in general, and adjusting the development time will change the amount of contrast. If your shadows are always blocked up, lower the EI, and if your highlights are blown out, reduce the development time. Alternately, if your highlights are flat, increase the development time.