On: Font Awesome, the pictographic font designed for u...

[tintin]

✔ it's also good practice to check unicode first. Arrows for example are available in all shapes and directions. ➜ So if there is an icon available in unicode just use that one.

[icebraining → tintin]

Support unicode doesn't necessarily mean the client has a compatible font. I couldn't see the "look of disapproval" emoticon (ಠ_ಠ) without having installed an appropriate font, for example.

[justincormack → tintin]

Not necessarily if you want the weights to match other icons. But in many cases this is the best option.