How can I make my Ruby script (not Rails) run anywhere?

Question

Hello,

I'm very new to Ruby. I've recently finished writing a simple script, which uses a bunch of gems. It works well on my own workstation.

When I copied the script over to my laptop, it stopped working, even though I manually installed all the gems. I think it may be due to version differences in the gems installed, but I wanted to know if there might be any other reason. So:

1) Is there a way to have Ruby automatically install all of the required gems for a script, in their correct versions?

2) Could there be any other reason for the script running on one machine, yet failing on another?

Thank you in advance,
Mr. Rabid Cow.