Great question — answering as the UphillTech team:
I'm currently working in our Eindhoven office and can see the runway from here ;) Hitchhiking is unlikely to work; there's no decent location to get picked up near the airport. The A2 highway is close, yes, but there's no parking lot or something similar. Furthermore, you're not allowed to walk on the highway itself. You'd have to post on the on-ramp, but there's no room to stop there. The train would be easy, and there are 7 buses per hour to the station. Pick the 401 (22 minutes; it uses a reserved buslane so no traffic jams); the 103 takes a horrible detour. Costs 3 euros one way, and you'll need coins for that. There are actually 4 trains per hour to Amsterdam; two of them go to Central...
Full answer by MSalters: https://travel.stackexchange.com/a/5893 (CC BY-SA 4.0).
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