In FAA land.....
Paragraph 4-3 and Figure 4-1 apply.
For standard helipads.....
"H" is to alined in the direction of landing/take off and a distinct "bar" painted on the surface to depict the preferred appproach direction.
Hospital Pad markings can be different and information on that follows the above referenced section as additional information.
https://www.faa.gov/documentLibrary/..._Heliports.pdf