This is an OpenGL port of a famous ZDoom source port. That means that you can expect here a great count of original Doom gameplay improvements, small settings and various options.
There are not so much graphical improvements in this port: simple particle effects for rocket trails, blood splashes and decals on the walls, flexible display resolutions system and high-resolution textures support.
Download and unpack port archive to the original game directory ('E:\games\Doom' in my case)
Run 'zdoom.exe' from the directory written in step 1. Select the WAD file to use if the game asks for it.
Open 'Options' from main game menu. Set 'Always Run' to 'On'.
Open 'Options'->'Set Video Mode'. Select an appropriate video resolution and aspect ratio supported by your hardware. Press 'Enter' to apply the settings.
Open 'Options'->'Display Options'. Select 'Sprites & Particles' for 'Blood Type' and select 'Particles' for 'Bullet Puff Type'.
Open 'Options'->'Display Options'->'OpenGl Options'. Set 'Rendering Quality' to 'Quality', turn on 'Smooth Sprite Edges', select 'Smooth' for 'Particle Style', turn on 'Shaders For Texture Warp' and 'Shaders for ColorMaps'. Ensure that 'Trilinear' is set for 'Texture Filter Mode' and '8X' set for 'Anisotropic Filter'.
Open 'Options'->'Display Options'->'OpenGl Options'.
Open 'Options'->'Sound Options'. Select 'Sample Rate' to '48000Hz' and turn on '3D Sound'.
Open 'Options'->'Customize Controls' to adjust your keyboard settings.
Open 'Options'->'Mouse Options'. Adjust 'Mouse Sensivity' here and turn on 'Always MouseLook'.