UIHint Attribute in MVC

When using a Display or Editor template, UIHint will tell it which template to use:

[UIHint("SomeTemplate")]
public class MyViewModel
{
     public string SomeProperty { get; set; }
}

If you create a Display template called SomeTemplate.ascx (since you are MVC2) in the Views/Shared/DisplayTemplates or Views/{Controller}/DisplayTemplates then it will use that template when you do:

@Html.DisplayForModel() // if Model is MyViewModel

or

@Html.DisplayFor(m => m.ModelProperty) // if ModelProperty is of type MyViewModel

edit
If you want to specify this on a property level:

public class MyViewModel
{
    [UIHint("Birthday")]
    public DateTime DateOfBirth { get; set; }
}

You could create a display/editor template called Birthday in the DisplayTemplates or EditorTemplates folder in either /Views/Shared or /Views/{Controller}. Then when you do:

@Html.DisplayFor(m => m.DateOfBirth)

or

@Html.EditorFor(m => m.DateOfBirth)

It will use the template specified in UIHint

UIHint can only be used on a property not on a class declaration as Dismissile states. I am using MVC3 so this may have changed from MVC2.

"Attribute 'UIHint' is not valid on this declaration type. It is only valid on 'property, indexer, field' declarations"