As how I understand it at the moment, to easily flash your Android Device with custom ROM’s, It’s best for you to first flash it with a custom recovery. Before you can do this, you got to make sure that your device’s bootloader has been unlocked (https://www.dc-unlocker.com/free-huawei-bootloader-unlock-tutorial).
The recovery that worked best for me is TWRP and can be found here: http://teamw.in/project/twrp2/170
An alternative way of doing this can be found here: http://theunlockr.com/2012/08/29/how-to-load-a-custom-rom-on-an-android-device/
Once you have done that, you can very easily reboot your device into recovery (this can be done using ROM manger for instance). You will then come into the TWRP Menu where you can backup your system or flash a Rom on it.
You can find many custom ROM’s for the Huawei G510 in the link below:
Now the real fun can start!
I’ve tried out a few ROM’s including the GamerV2, fusionX and Cyanogen.