Hi Kath -
<<" Is there a map or do you just have to find out by trial and error.">>
Indeed, Lausanne is on a hillside. About 300 meters altitude change from the lake shore to the park near the top.
There is a way to help to do that using some Swiss Maps.
This one shows bus/transport stops very clearly, if you turn them on in the menu ( under Points of Interest/ traffic- the star in a circle). It does not show altitude, but it is very clear on the location of the stops:
Mouse over an icon for a station, and you get the exact name of the station/stop, as well as which routes stop there.
This topographic map is more complex unfortunately , but it does show altitudes. It is possible to turn on a map layer for public transport stops. I did.
The altitudes are shown throughout in meters, with the lake at about 374 meters.
In theory, Google Maps street view might help...I tried a couple of spots and it was not to useful for me, but, you may find it works for you.
Finally, I suspect that the Tourist Information Office might have a useful map ...worth a look, at least.
There is one office near the main station, at Place de la Gare 9.