The Iowa Secretary of State's website has a great search tool that will tell you what precinct you are in and where you vote. You just fill in your full name and zip code. You do have to already be registered to vote for this tool to work. The page is headed "Am I Registered to Vote?" but the results page will give you your precinct.
"Am I Registered To Vote in Iowa?":
See also, "Find Your Polling Place": http://www.sos.state.ia.us/elections/VoterReg/PollingPlace/search.aspx
For the Democratic caucus, there is also a search tool that will tell you where to go to caucus by your street address: http://www.iowafirstcaucus.org/caucus_finder.php
The Republicans do not have a search tool, but their list is at:
Note that voters in Precinct 41 (both Democrats and Republicans) were supposed to meet at Breitbach's Restaurant in Balltown for their caucus. Hopefully, there will be an announcement soon about an alternate site.
~ Allison, Adult Services