IPC have made a set of recommendations or a standard for industry. This is named IPC-2221 http://tinymicros.com/wiki/File:IPC-2221.pdf. But note this is for the industry. If you are planing on doing a home made PCB. Well then it is more a question about manufacturing Here is a good guide for this kind of PCB http://www.electricstuff.co.uk/pcbs.html. I may also support you with some more hints if you need them