To get the best soft proof for print you have to have two accurate color profiles in place.
A monitor profile which would be generated by a hardware or software calibrator during a monitor calibration—if you calibrated your monitor to something like 2.0 gamma and a 5500 K white point, a coresponding monitor profile would be generated for the OS so that the CS applications know what your monitor conditions are.
You also need an accurate press profile, which is usually assigned to a document on creation (Edit>Assign Profiles). The default is US Web Coated SWOP, which creates a lighter soft proof than US Sheetfed Coated.
If either or both profiles are off the softproof (View>Overprint Preview if your layout has RGB color) will be less accurate. So for exmple, if your monitor's gamma is 2.2, but the monitor profile has it as 1.8, and your press profile is US SWOP but the press is printing closer to US Sheetfed, you would get a soft proof that's too light.
Thank you very much for your answer
For the screen i have Spyder 3 Elite calibration tool, will that work, can the profile be converted and used by Adobe programs ?
The press profile, will the best be to contact the print house and get it from them, or get them to tell me what they use ?
All the best
can the profile be converted and used by Adobe programs ?
Your OS handles the monitor profile, so in OSX you would see the profile generated by the calibration in System Prefs>Displays>Color>Display Profile and make sure it is selected.
You don't typically want to use the monitor profile as your assigned or working RGB space. The CS apps use the monitor profile to correctly convert and display your chosen RGB editing space (i.e., Adobe RGB)