You're going to need to create accounts at both Heroku and mlab, get the heroku toolbelt, create a database and get the full db url with the credentials.
- Have a meteor project you want to deploy setup on GIT
- if your not yet on git, you'll need to get up to speed before proceeding with this, of course you should be on git, versioning all your work, and luckily getting started is pretty easy. You'll also need a github account to follow this tutorial.
- Setup a Heroku Account here
- Setup a mongo lab account
- Install the Heroku tool belt
- create a new db on mlab
- create a new user for that db