B is for Beta Readers!
What is a beta reader? A beta reader is someone who reads your WIP (work in progress).
The purpose of a beta reader is to provide feedback--both with punctuation and grammar, as well as structurally with plot and characterizations--so that you can improve your WIP.
No, you don't need a professional editor to beta read for you. No, you don't need to pay someone to beta for you.
Ideally you'll want to ask another trusted writer who is familiar with your genre or someone who is an avid reader in your target audience to read your WIP. You wouldn't want an adult romance author to read and critique your middle-grade fantasy. They probably won't be familiar with the things that appeal to kids and may end up questioning and/or not understanding your fantasy world. That's not to say it's impossible for them to provide a valuable critique, but if you can, you should try to find someone who understands and frequently reads your genre. Usually it's good to swap with another writer, so that's just another reason to ask someone who writes in the same genre/age group as you.
It's also best not to ask your mom/dad/sister/brother/awesome-family-relative or BFF to beta read for you. Sorry to say, but they cannot be objective. Plus, it also puts them in a really tricky situation. If they LOVE it (which most of the time is the case), it's because they love YOU! But if they hate it, and are brutally honest with you, it could make for a very awkward family dinner.
"Pass the potatoes please."
"These potatoes? I thought you HATED potatoes. Maybe it's just MY potatoes."
"Ummm...I think I'll stick with the salad instead."
"I KNEW it! You HATE MY POTATOES!"
Save us all from a potato incident. Okay? Don't ask the family. Or friends. You seriously don't want to see a BFF example (ahem...EX-bff!). Trust me.