How to care for your compost pile

Once your pile is built, the only maintenance it needs is water and aeration.  The bacteria you have working for you are just like most other creatures on earth.  They need water and they need oxygen.  If the pile dries up, the decomposition will just slow way down.  If there is no oxygen, then the anaerobic bacteria will get to work.  These are the bacteria that don't need the oxygen to work.  If this is what you have going on, your pile will smell really bad.  This is not what you ideally want to have going on.
If you chose a good location, you may not have to water except on the really hot spells.  Compost is good at holding water so if it rains often enough, the pile will hold an adequate water supply and won't need much help.
If you keep the size of your pile about a 3 foot diameter, that helps greatly with the aeration of the pile.  If it gets much bigger, the surface area to pile ratio is greatly reduced and there is less available oxygen for your pile.  Either way you will need to aerate your pile to some extent.  The smaller piles are less material to move around and are therefore easier to aerate.  The most common method of aeration is a pitchfork.  Dig in and throw your pile around.  Try to get all of the drier outer material closer to the inside so it can start breaking down too.  They do make fancy tools to aerate your compost, but I have found that those work well for a bucket composter or for the edges only of your pile.  They don't get the heavier innards of your pile very well.  A good old fashioned pitchfork will do the trick perfectly.