Some recommend being a bit more implicit with the path structure. So
more along the lines of,

require File.join(File.dirname(__FILE__), '..', '..', 'Dir1',
'File1'))

File.join will apply the proper file separator for any given platform
running your code. Btw, there is no need to put the '.rb' extension -
it is implied.

I have been meaning to finish my 'relative require' gem, http://elreq.rubyforge.org,
that allows you to just do the following,

require '../../Dir1/File1'

Which I find much nicer, cleaner and easier. The gem is finished, I
just need to publish it. I'll do that this weekend.

Kevin