I am by no means a spoon expert. I just started using them early this summer and they are all I have used 99% of the time since and I have a ton to learn but at the same time I feel like I have progressed well so far and I am having more success. I can't speak for trout because I am yet to fish for them with spoons. But bass yes.
For me it has taken trial and error to dial in the right size spoons. I primarily have rotated from 1/8,1/4,1/3 and I keep several different shapes, colors, and designs with me at all times. I try to match the size with the bait fish in the lake. Small fat head type minnows are what I see in the lake. I love the cleos and that bass in my avi I caught in Aug with a tiger striped 1/3 cleo wigl dancing girl. The past month or so I have switched primarily to kast master type spoons and side winder type. They have much tighter action and I think they can nail a distressed bait fish to almost a T and I have success with them. If I am not having success with one type I will try something else. On saturday for example, I was using a very small under 2" silver/chrome weber champ which is like a kast master design and is so small I can't even get a weight reading on my digital scale. I figured it might be the perfect size and design for one spot I fish and I did not get any bites on it after trying for about an hour. I switched to a kast master design brass spoon that is a 1/4 and the bass wouldn't leave it alone all morning. So it was the same exact style but slightly bigger and a different color and it seemed to make all the difference. And it seems like I can almost always find a spoon that gets fish biting
Right now I am have been doing a pause when I retrieve the spoon after a few turns of my reel. If you keep your pole tip up high when you reel in and then when you pause you drop the tip a bit to create slack so when you pause the spoon flutters down deeper like a distressed bait fish. If you keep the line tight it won't ' dance ' down deeper the right way. It just sinks basically.
Hope this helps some and good luck!