My wife is my alpha reader. Besides being smart, intelligent, beautiful, good-looking, and hopefully reading this post, she is very well-read. Her natural tastes align fairly well with the stuff I write, which is also helpful. And she knows me well enough to understand the style of critique that is most helpful to me.
An added bonus is she's handy. I just have to ask her to read something, or lay it out on the table. No chasing her down, no emailing or (shudder) snail-mailing. We can talk face-to-face, which is the best way for me to benefit from her insight.
Often times, complaints she has about a story are symptoms of a problem she doesn't have the language for, or quite know how to pinpoint. But between the two of us, we can work out the root improvements I can make.
For instance, the classic "bad ending" which generally indicates a poor beginning. Or "what happens here is confusing" which is usually related to incomplete world-building. And so on.
One of the most interesting things for me about this process, though, is when she explains how she imagines the characters and worlds in her mind. Or her understanding of the meaning or significance of some of the symbolism. Often, it's completely different than what I had in mind writing the story.
Not wrong, mind you, just different. Because I took to heart Stephen King's advice to leave room in the story for the reader, I don't usually go into much detail about clothes or physical appearance (or any, sometimes). I leave out all but the descriptions that are key to the plot, or anchor dramatic moments. I want my worlds to be "just real enough."
And sometimes, when I'm really lucky, I not only have something I didn't realize I put in pointed out to me, but I see where I can expand on it and make the story better.
So, here's my proverb, newly minted - Leave room in your heart for love, room in your wallet for money, and room in your stories for your readers.