Anything I should do before starting to install OFP?

Yes. If you have any previous version of OFP installed, including the demo or the press release, I recommend that you do a full uninstall of that first, including making sure that any residual files and directories no longer exist after uninstalling. If some do exist, delete them manually. After uninstalling, I also recommend rebooting your PC before starting to install OFP.

Make sure you have the latest level or edition of your Windows version. Also install the latest driver versions for your graphics and sound cards. If you have a proprietary mouse or pointing device, make sure you've got the latest drivers installed for that, too.

Got Windows 2000 or Windows XP? Make sure you have Windows Administrator rights authority levels when you install OFP.

Finally check the Microsoft DirectX page to make sure you have the latest version of DirectX installed. If not, download it and install that before installing OFP. After installing DirectX, I recommend that you restart your computer and run DirectX's DXDiag utility to confirm that everything tests out correctly.

If for some reason you need to uninstall DirectX (e.g., to digress to an earlier version of DirectX because the latest one causes problems), take a look at DirectX Buster or at DirectX Eradicator.