Locate the TemplateContent element in the .vstemplate file for the template.

Add a CustomParameters element and one or more CustomParameter child elements as children of the TemplateContent element. For example:

<TemplateContent>
    ...
    <CustomParameters>
        <CustomParameter Name="$MyParameter1$" Value="MyValue2"/>
        <CustomParameter Name="$MyParameter2$" Value="MyValue2">
    </CustomParameters>
</TemplateContent>

Use the parameter in one or more of the code files in the template. For example:

string Value1 = "$MyParameter1"
string Value2 = "$MyParameter2"

When a project is created from the template, the values set by the Value attributes of the CustomParameter elements corresponding to the parameters will replace the parameters in the code files.