One important thing is that there are a lot of different kinds of editing, and it's a good idea to have them go in the right order if you want to avoid a lot of wasted work. 
 
 I haven't gotten entirely through editing with any of my writing but short stories, but I've gotten to various stages in several of my novels. 
First off, there is big editing. Huge plot holes that need to be fixed, large sections that need to be removed or added, characters that need to be taken out or added in, structure flaws, and things like that. There are very few people who are good enough that they can write a book and have nothing major that needs to be changed to make it the best it can be, especially people who are fairly new to writing novels (new, as in, they haven't completely written, edited, and published three or four books already–like me 

). Whether or not you want feedback for this kind of editing is up to you, really, but it is worth noting that, generally speaking, the published and experienced writers say that they need and use outside feedback for macro editing, and it is the new or unpublished writers who tend to 'not need it'. 

 As I said, this quite generally speaking, not a law or rule or anything, but–it is something to be aware of. No matter how much you know about your novel and about novel writing, outside feedback can be very helpful. 
So, that's where I start. I would do macro edits myself, all the ones I know about without telling, before letting anyone else give feedback. 
Then the next step I do is basically the same thing, just in more detail...asking questions like 'is this scene optimal' 'is this character acting like he should be' 'is the description in all the right places' 'does the tension have the right pattern', stuff like that. 
And then I get even deeper, and start moving towards stylistic stuff rather than story dynamics...whether scenes have good flow, whether the dialogue is good, so on. 
And then comes actual copy editing – fixing errors and such. This is one level of editing where having someone else do it as well as you is invaluable, or so I've heard from most of the resources I've found...no matter how good of an editor any one person is, more than one person is essential to getting a manuscript edited well. 

 Some people hire, some people ask friends, but it's a good idea to do it. 
And outside feedback is helpful at most of the stages, really. When and how often is mainly up to the author and the novel he's writing. 
isaac-sky wrote:
Did you just finished the novel and it is already editing? 
I recommend you to take a break and "forget" the draft for a week or two. After some time you can see the novel in a more wide point of view.
Very true.