Here are both modern and period sources for fighting. Modern fighting is specifically focused on SCA combat style.
Fighting and Training with a Spear. These are the notes on a spear-fighting class taught by Count Arlof.
Here are two excerpts from Fiore, both specific to spear-fighting.
The Poem of the Pel: This 15th century poem describes the skills required for the successful warrior or knight.
Here are a few resources for more information on fighting.