With GE you do Immigration & your customs declaration at the kiosk. You scan your passport, scan your fingerprints and confirm the flight you arrived on and then answer the customs declaration info. It's a list of "yes" or "no" questions. After completing that a receipt is printed out. You get your bags and head to the exit where you handover your receipt. If you get selected for secondary you'll have a large X printed on your receipt and the agent will question you and/or inspect your bags. On a trip back from Mexico with my family my parents didn't have GE yet but my Brother, Sister in Law and I did. I was back in my apartment in Manhattan (from EWR) before my parents were done with Immigration & Customs.
http://www.cbp.gov/newsroom/video-ga...s-global-entry
Edit: Some airline programs & credit cards cover the cost of GE. Nexus is 50$ for a 5 year enrollment but you have to do the interview at a border location & have to be able to pass the Canadian requirements too (no DUI ect).