domain name system - Best Practices in Speeding-up DNS Propagation

I
recently changed nameservers and it has been 24 hours since.
Some of my
visitors are complaining they are still viewing the old site while some are already
seeing the new site. Is there any way to speed-up the DNS propagation without updating
the hosts file of each of my
visitors?

Are there any best
practices when it comes to changing nameservers to minimize this
problem?

Answer

DNS records doesn't propagate in the sense
that they aren't "pushed" from your server to other resolvers. What actually happens is
that when other DNS servers look up your domain, they cache the record for X
seconds so that they don't have to do another lookup for subsequent requests.
X seconds should be determined by the
TTL value on the record when it was retrieved from your name server. If you've already
changed the address there's nothing you can do but sit and wait. If you had planned this
in advance, you could have lowered the TTL
value.

Some larger DNS resolvers cache longer
than the TTL, which is a violation of the relevant RFCs (but they don't care). If you
can track this issue down to a few name servers, you can email the operators and ask
them to invalidate the cache for your zone so that they'll stop using the cached (old)
record.

Honestly, though, unless this goes on
for an extended period of time, it's probably just as well that you sit tight and wait
and plan a better migration for next time, since the damage is already
done.