Over time, you'll likely see your lens develop a couple specks of dust inside the lens. This isn't uncommon, and 99% of the time, won’t affect your image quality at all. However, for the neat freaks out there, it'll become a big issue for you, and you'll want to send your lens in for cleaning. Lens Rentals shows us how they do it.
As a personal warning, I recommend letting the professionals handle this. One small mistake could turn your expensive piece of gear into a paperweight, so hand it off to the people who know what they're doing. However, if nothing else, this break down of the process looks really cool.
Lens Rentals does a great job of making the process look deceivingly simple, using just a small screw driver, and a couple prying tools, they're able to get into the innards of a Nikon 24-70 f/2.8 AF-S, Canon 85mm f/1.2L, Canon 100-400 IS L and more. Check out some of the pictures of the process below, and be sure to check out their full blog post to see even more gear getting a tear down.