Arrival info Lake Constance

Multiple highways lead directly to Lake Constance:
A81 Stuttgart-Singen and continue as B33 to Constance or via A98/B31 to Überlingen
A96 Munich-Lindau
A7/A96 Hamburg-Würzburg-Lindau or A7/B30 via Ulm to Friedrichshafen
in Germany,

A14 (toll) via Arlberg tunnel (additional toll) to Bregenz
in Austria,

A1, A4, A7 and A13 in Switzerland (toll).

In Switzerland, you need to buy a yearly vignette before you get on the highway. In Austria, there are also 10-day and 2-month vignettes. You can get the vignettes in the border regions at the gas stations as well as directly at the border crossings.
Especially on the B31 on the northern shore of Lake Constance, there is a lot of traffic. Same goes for the greater Stuttgart area. For the country road from Arbon to Kreuzlingen along the Swiss southern shore, you also need a lot of patience. The same applies to the country road from Lindau via Bregenz to St. Margareten. In short: At Lake Constance, it is often slow going by car in the summer.

Zurich (ZRH):
Pro: perfect rail connection, frequent direct connections to Konstanz by train, internationally well connected. Recommendation!

Friedrichshafen (FDH):
Pro: Extremely short distances. By train you can easily get to the city station. From there, if necessary, continue by train to Lindau or Radolfzell, by bus to Constance or to the train station port (to continue with the ferry to Romanshorn or the catamaran to Constance) or directly to the hotel.
Con: Unfortunately, the airport offers for some time only a few destinations, including Frankfurt (FRA) with Lufthansa, London Gatwick with EasyJet and some destinations in the Balkans with Wizz.

Frankfurt/Main (FRA):
Pro: International hub, very well connected
Con: Lengthy onward journey by train, e.g. via Offenburg to Constance. Especially on weekends, the trains of the Black Forest Railway are often full.

Stuttgart (STR):
Pro: reasonably satisfactory rail connections
Con: only a few destinations accessible by direct flight

Basel (BSL):
Pro: some international direct connections, including EasyJet
Con: no direct rail connection, shuttle buses to Basel SBB/Basel Badischer Bahnhof, from there by train via Zurich or Radolfzell (slow).

Karlsruhe/Baden-Baden (FKB):
Pro: small airport, frequently used by Ryanair
Con: few connections, no rail connection, shuttle buses to Baden-Baden, from there on via Black Forest train to Constance

Memmingen (FMM):
Pro: Small airport with some interesting connections
Con: No rail connection, mainly approached by Ryanair

Geneva (GVA):
Pro: Many international connections, e.g. with EasyJet.
Con: relatively long train journey necessary in the connection

Altenrhein (ACH):
Pro: compact airport directly on Lake Constance
Con: hardly any connections

Tip: With skyscanner.de you can easily find cheap flights. Especially the function 'Add nearby airports' facilitates the search.

Direct connection by train to Lake Constance are unfortunately few. Via Karlsruhe/Offenburg you can get directly to Constance with the Black Forest Railway. From Munich you can get directly to Lindau, from Stuttgart occasionally directly to Constance, better to Friedrichshafen with Deutsche Bahn.
Via Zurich, the Swiss Federal Railways (SBB) will regularly take you directly to Konstanz, and from Basel you can take a slow regional train to Friedrichshafen via Radolfzell. From Vienna there are occasional direct connections to Friedrichshafen, more frequent to Bregenz with the ÖBB.

Tip for northern Germans (without a bike):
ICE 75 Kiel-Hamburg via Frankfurt to Zurich (direct connection) and from there with a change directly to Constance.
ICE 73 Hamburg-Zurich (direct connection) and with one change further to Constance

If you bring your own bike, please be sure to note the various conditions for taking bikes on the train. On some routes you need to reserve in advance, on others just buy a separate bike ticket. So it's best to find out in advance about the options for taking your bike on the train!

Useful info on taking bikes on the train:
https://www.bahn.de/rad-nahverkehr
https://www.bahn.de/fahrradkarte-fernverkehr
https://www.sbb.ch/reisehinweise/velos
https://www.oebb.at/fahrradmitnahme

Many long-distance bus lines offer direct connections from numerous European cities, including Konstanz, Friedrichshafen, etc.. Two of the largest providers are Flixbus and Eurolines. Constance and Friedrichshafen, for example, are easier to reach from Munich by long-distance bus than by train.
Also in the long-distance bus you usually have the opportunity to take your bike. However, there is naturally only limited space for bicycles on the coach. That's why you have to book the bike transport in advance with the major long-distance bus providers.