A few weeks ago I started a sourdough starter. I wasn't sure if it was going to work, I tried it once a few years ago and it went funky not yeasty soo....
It was very simple and worked even in my rather cool kitchen.
Have a reasonably sized container (I'm using a 1.5 ltr preserving type jar) add 1 cup of WW Flour and 3/4 cup water stir and put it aside until tomorrow.
add 1 cup flour and 3/4 cup water again stir and put away till tomorrow again
Your mix should be quite wet and have bubbles by now. though if your kitchen is very cold this could take a little longer!
take half of the mix out add 1 cup of flour again and 3/4 cup of water. Stir it again and scrape the sides well. put it away again till tomorrow
If you are lucky your mix will have risen (but if not just keep going it could take a little while if its cold where you are!) if it did rise you can start making bread. Again remove half (save it for your 1st bread) add 1 cup of flour and 3/4 cup of water. your mix should be ok now to use daily for bread. it can be kept in the fridge and fed weekly (remove half add 1 cup flour 3/4 cup water)
*It is easiest to have a see trough container so you can check for any activity
*Best not to use metal, some metals can react with the starter
*a sloppy starter is easier to deal with than a drier starter.
*It can take up to 2 weeks to get it going, if you live somewhere cold don't get discouraged if you don't have bubbles on day 3!