In general, Pickaxe is our style manual. Make your code look like theirs. 
The following is mostly elaboration; exceptions are marked as house style.

* We use two spaces for each indentation level.
* Calls to "return" are allowed (but not required) on the last line of a method. 
  (house style)
* Don't use braces to span more than one line. Use do/end intead.
* Don't use do/end on one line; use braces instead.
* We prefer single-quoted strings when string interpolation is not being used 
  (or for other purposes, such as quoting single quotes). (house style)
* Instance variables holding ole objects should have 'ole' in the name. (house style)
* In general, Watir names (methods, classes) should follow what HTML or 
  JavaScript uses. These have precedence over the OLE API names. (house style)
* Parameter names should be descriptive and accurate. Always. Same is true for 
  local variables, but more slack is allowed.
* Single-letter names for local variables are allowed when they have limited scope 
  (and aren't parameters).
* No extra whitespace!!! No more than one consecutive blank line. 
* Never more than one consecutive space (except indentation).
* Argument lists are set like English (one, two, three) -- (except parens are 
  flush with method name, unlike english). 
* Method calls with no arguments don't require parens() and it's strongly 
  prefered to omit them.
* Method calls with args that don't actually need parens (for syntax) don't 
  require them either (for style).
* However: use extra spaces with vertical bars. Thus:
    (1..5).each {| n | puts n}
* Also, always uses spaces with operators. Thus:
    a = b + c if d == e
* Exception:
    def foo(bar=true)    
* And of course:
    def bird_bath= foo
    
Capitalization rules -- Straight from Ruby Style:

method names -- lowercase, use underscore between words. always!

instance variables -- same as method names (except with a @). always!

Class names are constants so they must start with Capital (syntax error otherwise).
Use StuddlyCaps for multiple words.

Studdly_Caps_With_Underscores are never, ever, ever correct. (But you get points for effort.)

camelCaseWithLowerCaseStart is never, ever, ever correct. Not for anything.

File names -- use underscores (sorry Brian), all lower case