I've commented before:

Use ViewNX2(for D200 files, very good program)

In VNX2, start from the top(RHS Pane), program defaults to the Metadata tab(which is actually a good thing! .. I'll explain later). On the RHS click the Metadata tab to close it, and it will reveal all the tools in the Adjustments tab.
From there you see the exposure, WB, and various other adjustments tools. Start from the top and work your way down as required.
For me, it's usually ends with choosing a Picture Control that suits, sometimes Vivid, sometimes Portrait .. it depends on how the image was exposed, and how harsh/soft the light was at the time of exposure.

Note, once you set the Picture Control, and lets say you used a contrasty Picture Control like 'Vivid' .. it then pays to use the finer adjustment tools below this named contrast/brightness/highlight/shadow .. don't use the sharpness tool tho(reason is that it's very coarse!)

You could try D-Lighting tool and colour booster, but I don't like the way they operate, you can do this later in Gimp .. it's up to you, but ViewNX2(ie. the raw file converter, is to get the raw file close to being edited on a very subtle scale).

ViewNX2 will not clone/heal, or manipulate pixels in hideous ways(like Ps, GIMP, etc) .. it's a basic raw file editor/converter.

Once you have the raw file very close to how you want it to look, you then use a short cut link (that you create) to GIMP to edit a tif file in GIMP. You don't need to go through the additional steps to create a tif file, it will do that for you.

In VNX2
1/. look at the upper toolbar, find the Edit tab, scroll down to the Options link. A box will open up once you do this.
2/. you may or may not have any open with links to start with(it depends on how it was installed). With this box open, on the LHS section look for the Open with Application setting. Click this
3/. once you click that if there is nothing listed in the larger central area, you have no apps linked. Look for the [Add] below the larger area. Hit that.
4/. it varies on what happens here, and you need to know where all your programs are installed, if you have a 64bit PC, or 32bit .. etc. If no applicable programs populate the list when you hit [Add], then click the [Other] button.
By default, it assumes you're in a 64bit OS environment, so you're using 64bit programs. If GIMP is 32bit only, you won't see the link to it, you have to navigate to find it. So, GIMP will either be easily found, but if your PC is 64bit(most are nowadays), you need to navigate out of the Program Files folder, and into the Program Files(x86) folder, if GIMP is 32bit only. I dunno how your PC is setup.
5/. once you find your way through all of that, you need to locate the .exe file for GIMP, and click on that for this to work. Once you find the GIMP.exe file, double click on it, it's then is added to the list of Open with programs.

if you can successfully get through this, now in ViewNX2, once you've added your basic raw edits, you can either rightclick the file on screen and Open with ... it will show you GIMP as an option to open the file with.
OR!! .. you can do one more step to make this easy too ..
6/. up high in the window there are icons to tools such as Convert, Movie Editor, etc, etc. there is a large blank section. Right Click the blank section and scroll down to customise. when you hover the mouse over customise, a long box will pop up, and you will see the Open with option to GIMP you just made, click that. This then creates a shortcut to GIMP you use as you need.

What all this does, is to allow ViewNX2 to create a tif file of the image(s) you select and automagically open it/them up in GIMP. You don't need to go through the steps to convert, it does it for you. All 16bit and no compression(ie. about as good quality as you want/need).

From there, you then play in GIMP.
I still reckon once you edit using CNX-D(for all it's woefullness) and use the Colour Control Point edit method, you won't find an easier way to edit only in NEF file mode.
That is, forget tif, it's a space wasting bloated file type that is long overdue for replacement as the default image file type of choice.
I edit the NEF files, saves a ton of HDD space.

Now back to the top(and why I use VNX2) .. still!
Back to to the topic of Metadata. I strongly urge you to keyword your raw files, and the best way to do this is via VNX2.
In the Metadata tab, scroll down just a little, and look for the section that is marked Tags -> Keywords.
it's a white box where you add words that get embedded into your NEF files. So for a photo of a Cockatoo, just for now, add the word Cockatoo into this box and hit the small save icon.
Doing this from the get go, will save you a world of pain later, when you have many thousands of images of stuff, and you can't locate them easily.

I can explain how to use this metadata stuff in another thread, and you don't need much in the way of software to help with that.