My favorite place in Vietnam. It is true for any country that it is in the villages that you find the best scenery, the friendliest people, the yummiest food and the awesome hospitality. It was a 6 hour bus ride from Ha Long to Ninh Binh but feels like a different world altogether. The landscape is dotted with krast landforms, lily ponds and paddy fields. The homestay we stayed at was at Trang An and to wake up to the krast mountains and the pond at our door step was bliss. We just hired a bike (unlike Saigon, its the best way to explore the place) and rode around everywhere, stopping wherever we found a pretty spot. The 400 steps climb on Mua Cave to see the view is totally worth it. I felt bad leaving Ninh Binh and moving on to Hanoi to catch my flight to Bangkok.
Read up but dont book everything in advance, public transport is fantastic so you will get bus, train tickets easily. Keep your schedule flexible you might love some places and you might hate some.
Almost all places have happy hours (6 to 8) make use of that for cheap beer (I once had a pint of draught beer for as cheap as INR 15)
Taxi drivers are going to quote absurd amounts, just ask them to put the metre down and go
Pho is usually the best in cheap road side stalls, not in any fancy place. Also try the lotus stem juice
All the tourist spots have Vietnamese name so if you are exploring on your own and not using guides learn those place names in advance and it is more useful to learn phrases like "where is..." than hello/thank you.