Battery keeps running down, what is the best way

The new alternator may have a closed regulator draining the battery,put a volt meter,or test light in line with the ground cable,remove the ground cable,and put the test light clip on the ground cable,and the tip of the test light to the negative battery post,or contact,it does not have a post,If it lights the test light,and it does not fade off,then there is a draw,unplug the alternator regulator plug,see if that turns the test light off,if it does,then the alternator is defective,then if need to continue testing,remove the interior light fuse,completly,and then pull one fuse at a time,to see if the test light goes off,when it does,that is the circuit that is drawing the battery down.The clocks will pull to many amps sometimes and cause this also,be sure to disconnect the battery over night to make sure the battery is good also,so you wont be doing all this for nothing,and you may want to have the battery load tested.

I had the same problem with my truck, what I did to solve that problem was I changed out the bad alternator, and replaced the positive and negative cables. That seemed to do the trick for me

Disconnect the positive cable then connect a test light between the cable and the positive battery post. if the test light lits then you have a drain. pull the fuse one at a time which ever one get the test light off then that's the one has short.