How can I control how text is displayed programmatically?

I intend to add label and literal controls dynamically to a Placeholder control at runtime, but I also need to know how to specify the way in which the text is to appear.  I understand that I can specify things like bold, italic, and underline features by declaring them as true or false.  I also understand that I can control the color of the text such as with: Label1. ForeColor = System.Drawing.Color.Black.  But, I do not know how to specify the size of the text as: small, medium, etc. 
 Most importantly, I do not know how to indicate whether the text is to be aligned to the left, centered, right, or both.  I know that this is controlled statically between portions of the hypertext that is defined such as with: <p align="center"> and </p>.  But, I do not know how to specify which labels of text are to be aligned to the left, centered, or otherwise.  Can you help me please?
 Maurice