The Sites folder on OS X server should by default create an easy to find alias that jumps to the folder. If this isn't the case, you can also find the default 'Sites' folder a few other ways.
2: Another way you can quickly find you 'Sites' directory is by using the Server application for OS X. Launch the server app, navigate to "Websites" on the left side of the screen, select your site from the list a and click "Edit". To the right of "Store Site Files in:" you'll see an arrow. Clicking this arrow will jump to the appropriate directory.