Grain is an artifact that's organically unique to film and depending on who you are, it'll either ruin your shot like sand in your chocolate or it's a grimy, gritty mouth-watering sublimity.
Sitting in a busy hotel restaurant surrounded by chatter while writing a blog entry isn't what most people would call perfect. But amidst the blathering white noise, this is where I find it easiest to write. Some of my favorite musicians still release new albums on vinyl because they feel that the LP's imperfections or "warm tones" enhance the listening experience and there now exists a black market for tungsten filament light bulbs because a 2700k LED light doesn't give a room that same comfortable and homely ambiance.
One of the main reasons I stick with film in my photography is because it's imperfections add character to any image and grain is the signature imperfection of film. Digital cameras are perfect, too perfect and they've given birth to a breed of photographer to which technical characteristics such as sharpness matters too much. They've sanitized and disinfected photography.
Of course, not every analogue photo needs gobs of grain. Some types of photo prefer a fine grain like the one above shot on Kodak Portra 400. A finer grain permits more detail which would otherwise be softened by a bigger grain. Some modern film stocks have such a fine grain that it's only noticeable when it's been scanned at an eye bleeding resolution. Fuji Velvia for one has been dubbed as "the digital emulator" as its ludicrously fine grain structure, strong saturation and it's extremely accurate colour reproduction is like that of a digital sensor. Google it and you'll see literally thousands of Velvia v.s digital comparisons.
Lets get back on topic though, there's no use discussing grain that you can't see. If grain is good, then big grain is better. Here's some ways you can pump up the grain in your photos...
Make a website with Mobirise