Something I stress very strongly is exhausting all of your free options before you pay anyone, including me, for help with a query, pitch, or WIP. Below are some amazing (AND FREE) helps for you to check out before you consider paying an editor. (NOTE! This is NOT a comprehensive list. These are just the ones that first came to mind when I was writing this post!)
– Query Shark: I consider myself to be a pretty harsh editor. I have nothing on Janet Reid, also known as the query shark. Read her entire site, and you will be an expert on what works in a query by the time you’re done.
– KidLit: Despite its name, the advice on this site is relevant for everyone. The post on showing vs telling is one of my favorite resources and comes recommended by several agents.
– #TenQueries/#MillionQueries/#InboxInsights: Several agents (including [most recently] Margaret Bail, Peter Knapp, Rena Rossner, Linda Epstein, Maria Vicente, and Connor Goldsmith) go through their query inbox and tweet about why they request or pass on said queries. TONS of great advice, particularly if you’re thinking about querying them.
– PubHub: This fantastic team of writers and industry professionals talks about everything you’d ever need to know regarding the publishing process and world in general.
– @QueryDrill: This project from @NotVeryAlice is a collection of experienced slush readers who will comb through your query and help you fix any problem spots. For free.
– Twitter in general: Find out where your favorite authors and agents get their advice from. Watch what they tweet. If you know who to look for, twitter (and the internet) is a freaking gold mine. Make sure you’re following reputable people who know what they’re doing, and you can’t go wrong!
Bleeding Ink, Inc 
This is wonderful information! Thanks so much for sharing!