As I have bought a Xiaomi Phone for my son, I need to move the Contacts from the old phone to his new phone.
Time to revisit how to do it.
1) The most famous way being advertised repeatedly is : To sync with your Google account.
Personally, I find it unreliable (it works sometimes but not all the time).
2) Export it.
I would suggest this way. Efficient, reliable, and foolproof.
First, go to your Contacts screen.
Press on the Menu button.
A screen similar to this will be shown.
Here, you have the option of Export to: USB storage, SD card or Sim card
I would personally advise exporting to SD card (if that is availble)
Click on it, wait for a few minutes, and it is done.
Slot your SD card into the new phone, reverse the process, and all your contacts will be restored.
Why is it better to use Export rather than to sync with Google?
Let me list down the benefit.
1) If you have setup the phone as I did, which is to create a dedicated album in the SD card, and store all the profile photo for the contacts within that album, once you restore the contacts this way, ALL the profile photos will be correctly pointed to the phone numbers. No extra effort needed to match those photos again. A real time saver.
2) Interestingly, all the Reminders you have painstakingly set up in your old phone will be moved to the new phone too. I find it really amazing. No need to click through the Calendar to set up it again.
Try it next time you change your Android phone. Probably you will like it as I do.