Its simple. Good light, good flow, stable parameters........
The real trick is the stable paramenters. That is the hard part. You can't necessarily just do that, its something that needs to be learned with experience. We can tell you how we do it, but in the end, you have to do the leg work, the testing, the learning how your tank behaves and how its running, the slight adjustments to be made to "coax" your tank in the right direcetion. I use that word because many try and "change" their tank, their paramenters. Parameters are never static. You just can't make your tank be a certain way. But with a little diligence, observation, and small adjustments, you can sort of juggle your tank to the range you want it to be in. The better you get at it, the smaller and more infrequent the adjustments are.
My tank is currently leaning in the ULNS direction. I'm trying to coax it back in the other direction. Not by dumping a bunch of crap in there, but by slightly increasing what I add daily. I know I'll know if its working in a week or two. No stress, no rush.