LIRR trains from Jamaica to Huntington run every 45 minutes/1 hr. up to around midnight and then less frequent after that. Take the Airtrain from your terminal to get to Jamaica station. You can purchase both your Airtrain and LIRR tickets there. Here's the link for the current Huntington LIRR schedule http://mta.info/lirr/html/ttn/huntingt.htm
LIRR trains from Jamaica to