Here is an example on writing tasks to your NFC tag. Here we take toggling Wi-Fi as an example.
They can be easily downloaded from Google Play.
Here below is the steps to set the tasks and write them to your NFC tags. The phone used is Nexus 5 and it should work well for other phones that support NFC.
To check if your phone supports NFC functions, go to this web page: NFC phones: The definitive list.
After the above steps, your NFC should have been encoded properly. You can just scan your tag to test if Wi-Fi can be turned on/off.
Noteworthy, you can add several tasks to a single NFC tag as long as it is within your tags’ memory size.