I'm using the following settings. Only use the SD Card overclocking if you have a good/fast (48mbs+) card.
force_turbo=1
#Overclock Settings
arm_freq=1350
over_voltage=6
temp_limit=80
core_freq=500
#GPU Based
h264_freq=333
avoid_pwm_pll=1
gpu_mem=450
v3d_freq=500
#Ram Overclock
sdram_freq=588
sdram_schmoo=0x02000020
over_voltage_sdram_p=6
over_voltage_sdram_i=4
over_voltage_sdram_c=4
#SD Card Overclock
dtparam=sd_overclock=100