Bus and metro
You can request a discount for a monthly or yearly pass from EPFL. More info here.
Train
The CFF website is very useful to get itineraries, combining bus, metro, train, boat…
Once you join EPFL, you can get a free “Demi-Tarif“, which will allow you to take the train at half-price (contact your lab secretary or see here). You can otherwise get an “Abonnement Général” that gives you unlimited travel all over Switzerland at a discount rate (ask your lab secretary or see here).