I write this topic to warn you some bad thing you may see when you visit Vietnam. I'm Vietnamese and i know many bad things through local news and other people. There are some advice to all visitors (absolutely except Vietnamese ones) if you want to have the best time to travel this country.
1. Always check carefully the price of everything you want to buy: you always negotiate price of products if you do not want to pay too much and ignore some stores which do not have listed price. If you have guides, ask them to follow.
2. Save your property: thieves are a lot in this country. Only a few second they can steal your smartphones (Iphone, Ipad are the most), wallets and something very expensive you wear. If it occurs, say very loud for local people help, try to see quickly and remember license plates if they drive motorbikes and ask police.
3. Stay away from shoeshine men because they can steal your shoes off your feet and then demand money for them.
4. Consider carefully if you want to eat street food: Banh Mi or Pho Bo are the best street food in this country. However even local people cannot guarantee where this food is safety. I usually see some news about food safety and the most are about dirty oil or beef or pork.
5. Always use map application from your devices to know exactly destination if you call a taxi or motor taxi.
Maybe there are some bad thing i do not mention about Vietnam in this topic but to conclude, please be very very careful if you want to visit this country.
I DO NOT SAY THAT THIS IS NOT THE GOOD PLACE TO TRAVEL BUT I'M VERY PROUD THAT MY COUNTRY HAS MANY FAMOUS PLACES WHICH ARE RECOGNIZED BY UNESCO AND VISITORS WHO ALREADY GO TO THIS COUNTRY TO VISIT AND YOU WILL NOT FORGET THE BEAUTIFUL OF THIS COUNTRY.