I agree that the shape of the code is what I start with too: the syntax-highlighted keywords stick out as anchor points when scrolling, and I know from indentation where sections start and end.

Example:

  if (...)
  {
     ...
  }
  else
  { 
     ...
  }

or

  loop
  {
     ...
  }

After I home in on the words then yes I will generally read left to right, top to bottom. But another part of imperative style is code is usually split into separate paragraphs of related functionality - so I can usually jump down whole paragraphs too.

The only other obvious variation I can think of is I will read bottom up when tracing the path a variable took to get to where I am currently looking.