I started and contributed to a long, very nerdish thread about uvb on another forum, that basically culminated in me saying I should start a company with a friend manufacturing UVB LED lighting, but we never did it. Lol. so I'll just stick to more conventional tips for this post.
There are a few things I do to get my potency as high as I can, within reason. you may not want to utilize all of them though, as they can be a significant tradeoff.
Okay, first, I use MHs with almost enough power to burn the plants, with unsealed, open hoods. Specifically, adjust a wing clone hoods. I set the reflectors to get the light as even as I can, and the lack of that layer of glass allows any uva & uvb produced to hit the plants. Now there are people who say my bulbs (sun pulse 3k halides) don't put out any uva or uvb, but they turn white plastics yellow, just like if you put them outside in the sun. That tells me they do. Flourescents and HPS, I've never observed that happening.
The tradeoff here obviously is with the open hoods vs ducted hoods, you just raised your AC cost dramatically, especially in warmer climates. So this wouldn't really be an option for larger grows.
Another thing I do is really pay attention to the flowering time. The strain I'm currently working with is advertised as a 6-7 week strain. At 7 weeks, it is pretty crystally. But at 8 weeks, I still wasn't seeing amber trichomes, and it was still growing new pistils. The longest I've let it go was about 9.5 weeks, and the quality was worth it. But when I do that, I really have to watch out, this strain grows bananas before amber trichomes! If I didn't catch that, it could ruin the next 3 stages growing next to it. I keep my eye on it and pluck off a few bananas every time.
And finally, the most significant, yet always most controversial, what I call "strategic leaf removal". I remove probably about 80% of the leaves over the course of the 8 or 9 weeks the plants are flowering. But this has increased my quality, and yield, by about 30-40% I'd say. I no longer have any popcorn buds, and buds need light to develop properly. If I didn't remove leaves, my crop would be garbage compared to what I get and expect now.