Pick a number of blank lines that will let you experiment with the text below hitting a page boundary. A good number is about 38. To test without wasting paper, use Print Preview or something like Microsoft XPS Document Writer.

Here's a Heading

Here's a paragraph that not only should have its lines kept together, but it should not be widowed from the heading above. This text is some idle rambling to help ensure that the paragraph is a few lines long. And the raven, never flitting, still is sitting, still is sitting on the pallid bust of Pallas just above my chamber door. Indeed.

For more information and context, see my blog.