Absolute Guide for 301 redirects

i want to do a 301 redirect for my old sites. want to move it to a new domain and do not want to lose all the link juice and SERP.
i need an ultimate guide on how to do it and avoid penalty for google since i am redirecting two of my sites to one. i also want to know how i can do it so as to preserve all the juice, organic traffic, SERp etc.