Instructions for making you own starter are below. Think of it as a pet: it has to be taken care of each day. Note the quantities given are the total you will need for the 10 day cycle. On the first day you only need 1/3 of it, so don't let shortage of ingredients stop you. I give US cup measures as this makes the formula simple: equal measures of flour, sugar and milk. Weighing it out obscures this symmetry - a cup of flour is not the same weight as a cup of sugar or milk. If you don't have proper cup measures, just use a measuring jug: 250ml of each.
Another important note is that metallic bowls and implements are best avoided as they can be reactive and kill off the yeast. Use plastic, glass or ceramic bowls and a wooden spoon.
When my batch reaches maturity I will post how I used it to make bread - assuming it is successful! And of course, at the same time I will be giving some away to my friends! In the interim, I'm making rye bread for the first time.
For a 10-day cycle (another cup each of flour, milk and sugar will be required on day 15 and every 5th day thereafter if you want to keep it going):
Mix the yeast with the warm water and let stand until a bit frothy - about 10-15 minutes. Thoroughly mix the flour, sugar and milk to a smooth, thick cream then stir in the yeasty liquid. Cover with a clean tea towel and leave to sit. This is day 1.
Day 2: stir starter
Day 3: stir starter
Day 4: stir starter
Day 5: add another cup each of flour, sugar and milk and stir until smooth
Day 6: stir starter
Day 7: stir starter
Day 8: stir starter
Day 9: stir starter
Day 10: Congratulations - your starter is ready! Remove 1 cup of starter to make bread, put 1 cup in a ziplock bag and give to a baker-friend. To the remainder add another cup each of flour, sugar and milk. You are now back to day 1.