Slice squash in half lengthwise. Scoop out the seeds with a spoon as you would a pumpkin. Then completely submerge both halves in boiling water and cook for about 20 to 25 minutes, or until the inside is tender to a fork and pulls apart in strands. (It is better to undercook if you are not sure). Remove, drain, and cool with cold water or an ice bath to stop the cooking. Then use a fork to scrape the cooked squash out of its skin, and at the same time, fluff and separate the squash into spaghetti-like strands. Discard the skin.
Reheat the squash strands by dipping with a strainer in boiling water just before serving.
You can also bake the spaghetti squash in the oven. Just scoop seeds out as described above and prick outside skin with a fork. Place skin side up in a baking pan with 1 inch water.
Bake 45 minutes or until tender in a 400 degree oven. Remove and allow to cool for a few minutes until they can be handled. Scrape with a fork as mentioned above and serve with stir fried sauce.