What I must know before I flash this Tablet?

[Titanic]

Hi everyone,

I have two Chinese tablets ( nonames) with Android ICS that I have already rooted

and I would like to flash a Custom ROM Jelly Bean on it.

I have never flashed a device before.

I dont know even what ROM is compatable to this device.

What I would need to know first before I would ever try to flash it.?

I really do not want to brick it.

Thanks in advance for all suggestions.