Munich Airport: Take the S-Bahn, not a taxi: S1 or S8 to Hauptbahnhof/Marienplatz takes roughly 40–50 minutes and runs frequently (together, about every 15 minutes by day). The airport sits in the outer fare zones: budget roughly €14–16 for a one-way/day-ticket option, depending on the current MVV fare. Choose S8 for the more direct run via Ostbahnhof; S1 is useful for the west side but takes longer. A taxi is poor value at roughly €94–106 to central Munich.
Memmingen Allgäu Airport: This is marketed as “Munich West,” but it is 110 km away. Take the airport shuttle to Memmingen station, then the regional train to München Hbf; allow 1½–2 hours door to door. A flight into FMM is only a bargain if the fare saving survives the extra transfer time and cost.
München Hauptbahnhof (Munich Central Station): The main arrival station for ICE and international trains, with direct S-Bahn access through the centre and U-Bahn, tram and bus connections outside. It is functional but under major long-term construction: use the signed north or south entrances/tram stops rather than assuming the grand east-facing entrance is open.
München Ost (Ostbahnhof): A genuinely useful east-side alternative, especially for trains via Salzburg/Austria and for stays in Haidhausen. It has U-Bahn, S-Bahn, trams and buses; S8 from MUC stops here, while S1 is slower.
München-Pasing: Useful only if your hotel is in west Munich or your long-distance train happens to stop here. It has S-Bahn and tram links; from MUC, take S1 and change at Laim, or use the slower direct S8 connection.