I recently learned that I don't need to buy packets of yeast to make bread. I can create a sour dough starter by utilizing the wild yeast floating around in the air. Take a look at this article for more information:  http://science.howstuffworks.com/innovation/edible-innovations/sourdough2.htm  What are the optimal conditions for creating a sour dough starter:   Are there optimal locations that has a higher concentration of wild yeast? (such as a cold/warm place or a place with alot/little light) What type of flour would work best? I also read somewhere to use acidic fruit juice to help accelerate the process. Is this true? And if so, why?  Some starters call for sugar and milk. What would these additions do?  
Some answers to your questions, based on my experience with wild sourdough starter in San Francisco:   70-80F is the ideal temperature range.  Below that the yeast incubates very slowly; above it, the starter will tend to ferment alcoholically. Do not leave the starter in direct sun.  UV light is a powerful sterilizing agent. An organic, cold-processed (i.e. stone milled) flour works best, because it will retain the maximum amount of its own wild yeast on it.  Cheeseboard: Collective Works likes to start with rye flour and gradually add bread flour, but they don't give a tested reason for this. I have never heard of using fruit juice in a sourdough starter.  I would be dubious about it; you'd be likely to end up with vinegar. Sugar is unnecessary for sourdough starters. Use purified water; chlorine/chloramine/ozone in tap water can kill your starter.   Finally, starters incorporating milk are fridge-only starters (as opposed to flour-and-water starters, which can be kept at room temperature if split frequently) which depend on the bacteria and lactic acid from the fermenting milk for part of their sourness.  They can be effective, and actually a good choice if you live somewhere with weak/poor wild yeast.  Note that you cannot transform a milk sourdough into a water sourdough, and using up 2 cups of milk every 2 weeks is more expensive than 2 cups of filtered water. 