How to lower soil PH?

I am new to this, the old me would have just bought a bunch of chemicals.  I have a PH of 7.8 and I have heard that the ideal range for a plant is about 6-7 and under 5 for blueberries.  What is the natural way to change PH?

Thanks

Add tons of organic materials - leaves, straw, manure, etc. 

How low can I get it by doing that?  Can I get it down to the 4.5 that blueberries like?

Probably not, but if you have pine trees, they like acidic soil and blueberries will do well with them. I dilute vinegar and water the blueberries about once a week.