You can find the guidelines here (in a box in the right-hand column).

The document also provides tips to gather support and promote your motion at the general assembly. We strongly recommend that all motions submitters read the document, even those who do not need to modify their proposals.

You can also contact the FSC Communications Unit if you need some advice on the messaging of your motion. Please drop a line to FSC Communications: v.taterra@fsc.org