Follow some of the links below.
An understanding of TEM wave propagation helps.
Learning the tools that come with Allegro.
Most reccomend a Signal Integrity Verification add on to simulate your critical signals.
Some interesting reading and links.
"Electromagnetic Compatability Engineering" Henry Ott ISBN798-470-18930-6
"High-Speed Digital Design" Howard Johnson & Martin Graham ISBN 0-13-395724-1
"Right The First Time" Lee W. Ritchey Free Download Right the First Time
And one of my favorites:
Especially number one, regarding clocks, which will apeal to all those that instead of using the
clock or crystal next to a device on a board, add a seperate board with long leads to achieve low jitter. The 10 Best Ways to Maximize Emission from Your Product
Reading up on DDR ram requirements (1,2 and3) and the various interfacing application notes is evry usefull, as this is one (if not thee) most used high speed interface and one of the most documented.
It will help give you an idea of what you have to constrain.