Hi there!
If you're sending Bitcoins and you don't know what fee to set - here's the most simple and easy way to set it right.
1. Go to: https://btc.com/stats/unconfirmed-tx
2. Check the number on the top of the screen - this is your best fee :)
Now some explanation. Here's how the https://btc.com/stats/unconfirmed-tx website looks like:
This is the current fee distribution in the Bitcoin network. The colours represent how much time transactions with the selected fee need to be processed.
On the screenshot you can see that currently almost all transactions have fee below 20 Satoshis per byte. So if you set it to 40 or at least 21 - your transaction will have priority over almost all other transactions that are currently waiting to be processed. Easy :)
Other useful Bitcoin posts:
How To Check Bitcoin Transfer Speeds
TradeBlock - Awesome Live Bitcoin Blockchain Viewer