Hire an Editor, Dumbass

Yeah, I'm talking to you, indie author.
Having your mom read over your manuscript isn't good enough.  Trust me, I speak from experience.  Moms are great at a lot of things, but picking apart their child's work isn't one of them.
My first two books were very, very poorly edited.  I did hire someone, but he was overworked and didn't do a particularly good job.  I found Cynthia through the mega douche Elle Casey's Facebook page.  She was an aspiring editor at the time, so I took a chance and gave her my novel THE GATE.  The rest, as they say, is history.
She has worked on all of my novels since.  Cynthia offers a plethora of options if money is an issue for you, but I would recommend getting the Detailed Copy Editing and Proofreading Package.  It will really cut down on the amount of typos that make it into your final manuscript.
I would also recommend getting a few sharp-eyed beta readers.  No single person can comb through a 100k word manuscript and find every error.  It's not going to happen.  Even if your editor has a 99.9% accuracy, that would still leave a hundred problems with your book.  Don't dick around with this.  Again, I speak from experience.
If it sounds like I'm shilling for Cynthia, it's because I am.  She rocks.
Actually, I don't even know if this counts as shilling... I'm outright telling you to use her service without pretending to be unbiased.
Whatever.  Go hire her.
Shut up.