After burning a disc, do the jitter test and the BLER test.
Lower is better. For Blu-ray, when doing the BLER test, you want BIS to be lower than 10 (maximum) and less than 0.50 (average). Small spikes are okay. LDC is sometimes very high, but BIS is low; this is okay.
A member by the name of luigough did some tests 3 years ago, to check on some old discs he had. If you look at the scans he posted on his own site, you can get an idea of what is good and what is not so good: http://goughlui.com/2012/12/05/recordable-blu-ray-disc-longevity-periodic-survey/ (he adds commentary about which discs have aged well, and which ones are going bad, which should tell you what is okay and what is bad).
Also, you can compare scans done on Panasonic (MEI) single-layer BD-R http://club.myce.com/f179/matsushita-electric-panasonic-mei-bd-r-sl-321135/
and TDK media (FTI makes BD-R using TDK’s technology. Some scans are of TDK’s own products, some scans are of FTI’s products, and some scans are of media made by other manufacturers. Posts will mention “Made in UAE” or “made by FTI”) http://club.myce.com/f179/tdk-bd-r-sl-273605/
…to scans done on Philips media made by various manufacturers: http://club.myce.com/f179/philips-bd-r-323117/
The Philips media is mediocre/bad/very bad; the TDK media is often very good (made by FTI/Falcon is often REALLY good); and the Panasonic/MEI media is very good. That will help give you an idea of good burns and bad burns.
For jitter, less than 13% is okay, but less than 10% is good. Less than 9% is very good.
TE/FE: use TE/FE to see if there are big problems with the surface of the disc. It is good to use TE/FE before burning, but can also be used after burning. If BLER tests and jitter tests seem bad, try TE/FE tests (and look at the bottom of the disc under a powerful light). If a drive suddenly stops burning [B]in the middle of a burn[/B] for no reason, sometimes a TE/FE test will show that the disc is hard to read/write, and a lower speed might help.