DNS propagation time - Myth overwhelms facts!

Check for availability of domain.
Allocate web space to domain and upload index.html or such other default file.
Book the domain.
Moment after click to complete domain registration, the website should be accessible either in your computer or through proxy service at kproxy.com / megaproxy.com . In case website is not accessible even after 15 minutes, either domain provider or space provider lacks real time service.
In order to fix up the problem location, try whois service at http://www.internic.net and, if necessary, at three more whois websites. In case domain is not listed at all the four whois websites, domain service is slow.
In case your domain is listed at at least one whois website, check up domain at http://tracert.com/resolver.html . In case domain does not resolve to an IP, hosting service is not real time.
15 minutes stated above is liberal waiting period. In practice, that should be 15 seconds.
That is applicable to new domains only. After you change nameservers of an existing domain, new domain information should be available at some whois websites in a moment. Website may take some time to show up.
Here is the test for realtime domain service :-
Log into into your domain account and modify nameservers - in case you do not know any valid nameservers, you may use ns1.everydns.net and ns2.everydns.net . Immediately, modify nameservers back again. In case of realtime domain service, you may modify nameservers every minute. In case of slow service, you may have to wait for two days between nameserver modifications.
In the same way, you may upload website instantaneously on receipt of hosting information. In case of slow hosting service, it takes "a few hours".