OpenStreetMap Schweiz, https://www.osm.ch/
Neuchâtel is about 90 mins by train from the international airports in Geneva, Zurich, and Basel. Trains from Geneva Airport run directly once hourly (last train to reach Neuchâtel about 9 pm). Trains from Zurich Airport run twice hourly directly or via Zurich central (until about 10 pm). From Basel EuroAirport, take the shuttle bus twice hourly to Basel SBB and then a train via Olten or Biel/Bienne (until about 9.30 pm). Tickets are CHF 50–60 one way; early bird fares are available through sbb.ch (watch out for the black % triangle).
While Neuchâtel is small enough to be walkable, it is built into a hill—getting to some locations can count as a full work-out. The conference venue is at lake-level, as is the inner city. The train station Neuchâtel Gare CFF is uphill (5–10 mins walk to the university and 10–15 mins back). It is connected to the university Swiss-style via a cable car (Fun’ambule) which leaves from the station’s concourse every three minutes. The buses 101 and 121 stop outside the main building (Stop Université).
If you are staying in a hotel, you will be issued with a local transportation ticket that allows travel on public transport throughout the Canton of Neuchâtel. If you arrange for private accommodation, bus/cable car rides are CHF 4.20 for a single ticket (CHF 2.10 for a short bus trip). Multiple-trip tickets are CHF 21 (6 for the price of 5) and need to be validated before each trip via the machines at the bus stops. Tickets are only available from vending machines; you cannot buy them from bus drivers.
For more information on getting to Neuchâtel from further afield in the canton, check transn.ch or sbb.ch. Hiring a bike might be an option; check out neuchatelroule.ch, which has a self-service drop-off spot right next to the conference venue (spot 117 UniLac).