What you want is a "beta reader." A beta reader can be a writer or an avid reader; their purpose is to point out flaws in your work. You want to make sure you're explicit about what you want from a beta, particularly if you cannot handle harsh criticism, if it's your first time, or if you want a smackdown that makes Gordon Ramsay look tame. (I tell my betas to be brutal.) Just make sure you get more than one beta reader to look at your story. Betas have opinions, and opinions are not always right, so you want more than one person providing feedback.
If you want to skip over your mom and get betas from other writers, I recommend offering a beta exchange. Your story for theirs. There are websites that help writers find each other, like Critique Circle and Absolute Write. I've even found betas on deviantart and fanfiction.net just by starting conversations with people whose interests are similar to mine. If you're not sure how well you'll like working with a particular beta, offer them just a chapter or short story to test the waters. I've traded betas with several random people and it's always gone fine.
As for how well a person beta reads, scifi author David Brin allegedly gives his manuscript to friends and asks them to make a mark on it every time they get up to do something else, including biological functions. This way, they don't have to be super-betas for him to recognize when the story slows down enough to release the reader. Also, one thing I've learned is that a person's own work doesn't have to be flawless for their feedback to be great. Keep that in mind when trying a new beta reader.