Kanger designed them as a disposable component, they're meant to be replaced when quality begins to drop. However, you can make them last a bit longer by doing a dry burn cleaning. Like Maoufan said, do a YouTube search. It's not something easily described in words, you need to watch someone do it.
You'll do a dry burn as often as needed. Which nobody can tell you, it's up to you and your standards for a good vape. Myself, I can drag a coil through the mud to China and back and as long as I still get halfway decent flavor and a bit of wisp, I'm not freaking out.
As for disposal, like I said they're meant to be used and tossed. However, if you're dryburning, there is a limit of how many times it can be brought back from the grave. Again, up to you in terms of quality.
And if you're asking about cleaning and reusing them, I'm guessing you're on a budget or they're hard to get. Look into rebuilding. Seriously. Takes about $20 for all tools and materials for a year supply, and it's not hard. Again, YouTube is your friend. Seriously, I've seen ditzy blondes and old grandmas with coke bottle lenses rebuild these. Just takes some practice.
And just FYI, pop a search before posting a new topic.
https://www.google.com/search?q=how...n+kanger+coils+site:www.e-cigarette-forum.com It's probably been asked before.