I have just added a post about understanding and fine-tuning the BSP tree parameters
The post was recently updated ,and can be found here.
I hope you find it useful!
Finally, keep an eye out for this thread (i.e. dates), as it's constantly being updated!!
More tips and Tricks:
Tips & tricks for architectural Visualisation: Part 1
Essential tips & tricks for VRay & mental ray
Creating Customised IES lights