ETH Zürich provides detailed information on how to get to the main building from the airport, the main train station and with a car (not recommended!), Google Maps does the same. So this is the executive summary:
From the city
You’ll be arriving at “ETH/Universitätsspital” either by Tram 6 or 10. The two different stops are towards the front entrance of ETH (mind you, it’s the same stop when going back to the city; the map tells you why).
Alternatively you leave the tram at station “Central” and use the recommendable Polybahn to arrive at “Polyterasse ETH” (towards the back entrance “Polyterasse”).
From the airport
Tram 10 takes you to ETH in 30 minutes approx exactly. Follow the “Tram” signs at the airport. Or follow the “SBB” signs for an “S-Bahn” towards the main station, then taking tram no. 6 or 10 to ETH (from “Bahnhofstrasse/HB” or “Bahnhofplatz/HB”) . Or walking across the river to “Central” to take the Polybahn.
Once inside, there are signs toward the conference venue.
We recommend buying day passes for the Zurich “City zone” 110; this contains “1-2 zones” and should cover most hotels. If you’re arriving or leaving from the airport, makes sure to buy “2-3 zones” for that day as the airport is in the next zone. More information about available tickets