I wrote a Rails Syleguide I use in my projects:
http://www.jensjaeger.com/2008/04/styleguide-for-rails-projects/

1) Which do you like better, YAML.load or YAML::load ?

I don’t have a strong preference.

2) How do you declare variables. E.g., a) array = [] or array = Array.new

I find that I rarely declare an empty array variable, often doing so is a sign you should be using an Enumerable method with a block. I prefer the [] style, and {} for Hash unless I’m doing something unusual, in which case the wordier style is clue that something weird is being done.

3) What’s your usage of single quotes and double quotes for string. Do you exclusively use single quotes when there is no interoperation?

In theory, yes, I try to use single quotes without interpolation, but it’s an easy (and relatively harmless) thing to backslide on.

As to the options in your gist post:

Multiple assignment on multiple lines. Always. It’s rarely a good idea to have multiple statements on a line in Ruby (some rare exceptions when the code is deliberately boilerplate). Multiple left hand sides is, I think, just a bad idea.

I have no preference between “size” and “length”

I would never have “return nil” as the last line of a method. I might do either of the other two options (just plain “nil”, or ending with the rescue), depending on which seemed more readable in the method, I don’t have a strong preference.

Personally, I think have indented “when” clauses in a case statement is more aesthetically pleasing but that is probably because I come from a Java background.

The only difference in my “style” is for methods with long attributes:

a_very_long_method_name(
argument1,
a + b,
arg_3
)

Although it uses more lines, I think the indentation makes more sense.

do_something and return if condition

that works as long as do_something returns true.

This practice should be avoided since in a modifier method (as “do_something” often is) the return value is seldom important.
But if the method returns false or nil, the code fails.

1) Which do you like better, YAML.load or YAML::load ?

2) How do you declare variables. E.g., a) array = [] or array = Array.new

3) What’s your usage of single quotes and double quotes for string. Do you exclusively use single quotes when there is no interoperation?

Please refer to http://gist.github.com/22117 . I wrote some options there.

As such, my position is: do not use get_ or set_ prefixes, and especially not _getter or _setter suffixes, with the usual caveat of use your best judgment in your situation.