#1, Check which address you're sending to:
This should seem obvious but it wasn't completely to me. I almost got scammed recently because I had downloaded and ran malware that swapped the bitcoin address I was sending to. The variant I got made the change very visible, but there might be types of this malware that can change it right as you paste it.
For checking receiving address (moving your funds to one address to another or moving your funds to address of others your trade with), please read:
It is impossible for a hacker to generate a private key which only changes a few digits of your public address.
Even vanity generators are able only to match a few characters together.
So you only need to check some characters, not all of them.
Even if it takes only a minute, it is not necessary imo.
You can check entire address if you have time, but checking few first and last digits likely enough, middle can be ignore.
Or you can check few first, last, and a little in middle of your address.
Of course, nothing bad if you check your receiving address entirely.