You should be able to find some in-depth strategies and build-orders online, but I'll give a short overview of what I remember:
Ra is terrible at fighting in the classical age, but really picks up in heroic and mythic. A common strategy is called a "fast heroic", where you aim to get into the heroic age ASAP and get a midgol stronghold up. Rain is commonly used to provide a large food boost in order to have enough to advance.
Ra is good at booming. Almost always you should be improving your economy and building cheap buildings to gain map control.
Much more in-depth guides:
http://www.rts-sanctuary.com/RTS-Sanctuary/showtopic=41938
http://aom.heavengames.com/cgi-bin/forums/display.cgi?action=ct&f=1,26431,0,all
http://aom.heavengames.com/cgi-bin/forums/display.cgi?action=ct&f=1,28266,0,all