no super secret but mayby:
see no texture is missing
have no materials you not need in the scene, c4d exports always all in material manager
use no search paths (in c4dprefs),or as few as possible
best all are absolute texture paths, or in local tex folder
use renderinstances where possible
avoid many procedural objects ,plain polygons or renderistances of polygons are faster in c4d.
see phong tags have normal values (less than 40 better less than 20 degree)
take care with maxon hair settings, avoid unneeded high setups.[/li][/list]
for sure not all, but a fewthings that can dramatically slow things down,at least in my expereince:)
cheers
Stefan