The two main elements that impact the appearance of texture in an image are the quality of light and its position. That means it doesn't only matter where you place the light relative to the surface of the subject you're illuminating, it also matters whether it's a specular, hard-edged source or a large, diffused softbox type of source. Each of these factors has a huge impact on shadows, and its shadows that create texture.
A frontal light source—one that's positioned very close to the lens—is not going to create many visible shadows. That shadowless on-axis illumination will flatten the appearance of texture because the shadows aren't visible from the camera position. Move that light 90-degrees in any direction, though, and suddenly you're creating a lot of strong shadows courtesy of light raking across the subject. It's those shadows that equate directly to enhanced texture.
Imagine your subject is a textured plaster wall. Better yet, imagine it's an impressionist oil painting hanging on that wall. With frontal light there aren't any visible shadows from the textured paint and plaster, but with a light 90 degrees to the side of the subject those tiny little bumps of plaster and paint will create strong, dramatic shadows. Somewhere in between purely frontal light and purely side lighting is likely to be ideal—unless of course you're looking to mask texture (with a frontal light) or make it over the top (with a raking side or top light).
Once you've got your light positioned, however, you've still got to address the quality of the light. As a larger, softer source, a softbox creates a wraparound illumination that creates—rather than the hard-edged well-defined shadows of a specular source—soft-edged shadows that aren't as dark or well defined. And that means a soft source is going to minimize the shadows that tip the viewer off about texture. Sound familiar, portrait photographers? There's a reason soft light sources look so pleasing on skin—they minimize the texture caused by bumps, blemishes and pores.
Even if you aren't adding lights to a given scene, these same principles apply. Landscape photographers, for instance, like to shoot at sunrise and sunset—partially because of the beautiful color of the light, but also because its low angle increases drama by enhancing texture. It's for the same reason that photographers often avoid shooting at midday; the straight above sunlight is fairly flat and shadowless, which isn't especially interesting. But flat and shadowless light from an overcast sky will minimize texture, which makes it appealing for some landscape photography circumstances. Even though you're not moving the sun around, understanding its quality and position allows you to shoot at the right time to create the affect you're after.
So what have we learned? That you should choose a hard-edged, bare-bulb style light source and position it closer to 90 degrees from the surface of the subject if you want to maximize the appearance of texture. To minimize it, use a large, soft light source positioned close to the lens axis. It's not an especially complicated procedure, but it makes a huge impact on the look and feel of texture in any picture.