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CloseShader declares Material properties in a Properties block. If you want to access some of those properties in a shader program, you need to declare a Cg/HLSL variable with the same name and a matching type. An example is provided in Shader Tutorial: Vertex and Fragment Programs.
For example these shader properties:
_MyColor ("Some Color", Color) = (1,1,1,1)
_MyVector ("Some Vector", Vector) = (0,0,0,0)
_MyFloat ("My float", Float) = 0.5
_MyTexture ("Texture", 2D) = "white" {}
_MyCubemap ("Cubemap", CUBE) = "" {}
would be declared for access in Cg/HLSL code as:
fixed4 _MyColor; // low precision type is enough for colors
float4 _MyVector;
float _MyFloat;
sampler2D _MyTexture;
samplerCUBE _MyCubemap;
Cg can also accept uniform keyword, but it is not necessary:
uniform float4 _MyColor;
Property types in ShaderLab map to Cg/HLSL variable types this way: