Look up
DDR routing or layout
PCI layout or routing
etc
each sub set of high speed layout has numerous design guides, look at the data sheets of the chips you are using and the manufacturers web sites, these will also be a good source of information. Each sub set will have its own requirements for timings, line impedance, branch lengths, timing requirements (length matching) etc.
below is a few useful links...when I get chance I need to update it, I tend to download useful documentation though.
With high speed design it helps knowing how signals propagate and some basic wave theory, ie electrons move at a snails pace 0.1mm/sec approx.