Setting up numbering in styles

I am trying to create a number of styles which link to the previous ones but I can't seem to get the numbering right. For example I'll have some headings under the style Heading 1 eg 1. North 2. South 3. East but when I try to make a Heading 2 style to follow that the numbering goes out so where I want 2.2 I have 1.2 instead. I can't seem to get the heading 2 to restart the numbering correctly.