Steps
1. Wash, peel and cut the tubers into chunks.
2. Place the tuber chunks in a bowl of cold water.
3. Wash the chunks for a few minutes.
4. Drain off excess water using a sieve.
5. Half fill a deep frying pan with oil and heat.
6. Test that the oil is hot enough for frying the french fries by placing some chunks in the oil. If the french fries burn within a five to ten minutes of frying then reduce the heat.
7. If the chunks take longer than 15 - 20 minutes to cook then increase the heat slightly.
8. Place small batches of chunks in the oil to cook. Remove when golden brown or yellow with a crispy outer layer.
9. Place the french fries in a sieve and shake to remove excess oil.
10. Eat whilst still hot, sprinkled with salt if required.

Source
Food and Agriculture Organization of the United Nations (1994), Utilizing root crops, RAPA Publication 1994/30, Regional Office for Asia & the Pacific Bangkok, Thailand