Newbie in scalability design issues

I have 3 exp in building website using java.I work on only single server.Website is not very scalable.I always wonder how ebay,youtube,monster handle traffic, giving responses within seconds.From the google i find this site and i hope i can also able to build very scalable website .I need guidelines from where to start ,what are the things we needed.I know that scalability comes through the use of distributed applications but don't how to implement it.
I see many website build in languages other than java so java is good choice for building high scalable website.