Why and how to lower the hydration of my starter?

http://www.thefreshloaf.com/node/13069/am-i-creating-low-hydration-starter-or-underfeeding

Also search under:   changing to a firm starter    or    liquid vs firm starter

The how is simply using mathematical conversions that are easy to find (and written in terms easier to understand than what I might put here). The why's require reading several articles and deciding what you want to do. Besides all the complex reasons involving the balance of critters in the starter (which affect vigor and taste), one simple reason to keep or change a starter to a lower hydration is to match a certain formula/recipe (or if you use a specific formula all the time). You can always make the conversion when you are bulking up the amount needed for the formula. Frankly, I think that the major reason most people keep 100% hydration is that the math is simpler both for maintenance and for conversion. It also happens to yield a good balance of critters in my opinion.

that you slow down the starter.  (be sure to take notes) That first feed might be better with a higher portion of starter to maintain a lower pH.  

For example: if you normally feed your starter (s:w:f) (1:2:2)  make the starter and water equal for the first feed (1:1:2)  With the next feed, the dough will be dryer when mixing.  

Keep the starter amount equal to or less than the flour amount.  It is also possible just to add more flour to the ripe starter and skip the water.   Just my two cents.