Before creating your registration guide you need:
the paper that you will be printing on (torn to the correct size)
your linoleum plate
a large piece of newsprint or low quality drawing paper (for the box method)
cardboard, foam core, or matte board (for the t-bar or jig method)
a pen
a ruler
elmers glue all or other glue (for the t-bar or jig method)
The first 5 minutes of this video demonstrates the basic box method, which is a slight upgrade to the "eye-balling it" method that you have probably already been using and continues on to demonstrate several other methods, including creating a corner jig.
This video demonstrates a four color reduction, but has an excellent hand-made registration tool; ideal for working with a multi-color process.