There's a number of threads here and elsewhere that offer up the opening "tweaks" and optimizations for the newcomer...
Besides the highly-addictive ROM flashing, there's the hacks/tips/tricks thread... well worth a thorough read, whether you flash a custom ROM or not...
http://forum.ppcgeeks.com/showthread.php?t=51532
Some others:
http://knguyentu.com/wordpress/2009/...900-unleashed/
http://www.samsung-omnia.org/how-to/..._next=next#new
Enjoy... I hope these help.