My wife and I are planning to use a Eurail Select passes for the majority of our train travel in Europe. As I understand it, once our passes are validated we can just hop on any train that doesn't require reservations. My question is about four trips we are taking that require reservations:
1) TGV from Lausanne to Paris
2) ICE from Paris to Saarbrücken
3) Sleeper from Munich to Venice
4) Eurostar from Venice to Milan
If we purchase reservations in advance for these four trains, is there anything we have to do upon arrival to the station? Other than allowing time to find the correct platform/train, is there any reason to show up early?