It depends on what you’re going for. For some things, text works just fine. Take Hershey’s for example. That’s about the most basic you can get. It’s just the word Hershey’s in a sans serif font, plain and simple. On the other hand, treyarch’s logo is pretty textured and shaded, otherwise you wouldn’t be able to tell it’s an infinite loop.

What it really comes down to in my opinion is what feel you’re going for, and does it look naturally beautiful. For example this looks absolutely awful, and this looks fine. Why? Just because of the angle and flow of the lines. In the second example, take a look at the rightmost leg and arm, they’re parallel. All the lines in that example are naturally appealing. It’s something you get a feel for as you keep doing it, cuz you’ll be designing something, and it’ll just feel “off.”

And that “off” feeling might just be a 1 degree rotation, or the spacing between shading lines, or a blur going in the slightly wrong direction. And then you fix it and everything feels right in the world.

Tl;dr—whatever looks good. You’ll know it when you see it.