Nerdtree - Reveal File in Tree

Check this out, it automates the sync operation, whenever you change buffer, the nerdtree will automatically refreshed itself (I copied from here with tiny modifications)

" Check if NERDTree is open or active
function! IsNERDTreeOpen()        
  return exists("t:NERDTreeBufName") && (bufwinnr(t:NERDTreeBufName) != -1)
endfunction

" Call NERDTreeFind iff NERDTree is active, current window contains a modifiable
" file, and we're not in vimdiff
function! SyncTree()
  if &modifiable && IsNERDTreeOpen() && strlen(expand('%')) > 0 && !&diff
    NERDTreeFind
    wincmd p
  endif
endfunction

" Highlight currently open buffer in NERDTree
autocmd BufEnter * call SyncTree()

This should also probably be just a comment. With the current version toggling NerdTree and using SyncTree causes NERDTree to be invoked twice. This modification seems to fix that problem:

" Check if NERDTree is open or active
function! IsNERDTreeOpen()
  return exists("t:NERDTreeBufName") && (bufwinnr(t:NERDTreeBufName) != -1)
endfunction

" Call NERDTreeFind iff NERDTree is active, current window contains a modifiable
" file, and we're not in vimdiff
function! SyncTree()
  if &modifiable && IsNERDTreeOpen() && strlen(expand('%')) > 0 && !&diff
    NERDTreeFind
    wincmd p
  endif
endfunction

" Highlight currently open buffer in NERDTree
autocmd BufEnter * call SyncTree()

function! ToggleNerdTree()
  set eventignore=BufEnter
  NERDTreeToggle
  set eventignore=
endfunction
nmap <C-n> :call ToggleNerdTree()<CR>

Chen Rushan's answer + the comment worked perfectly well for me only except when the tree is activated. This settings will reveal the current file in tree when the tree is opened.

" Check if NERDTree is open or active
function! IsNERDTreeOpen()
  return exists("t:NERDTreeBufName") && (bufwinnr(t:NERDTreeBufName) != -1)
endfunction

function! CheckIfCurrentBufferIsFile()
  return strlen(expand('%')) > 0
endfunction

" Call NERDTreeFind iff NERDTree is active, current window contains a modifiable
" file, and we're not in vimdiff
function! SyncTree()
  if &modifiable && IsNERDTreeOpen() && CheckIfCurrentBufferIsFile() && !&diff
    NERDTreeFind
    wincmd p
  endif
endfunction

" Highlight currently open buffer in NERDTree
autocmd BufRead * call SyncTree()

function! ToggleTree()
  if CheckIfCurrentBufferIsFile()
    if IsNERDTreeOpen()
      NERDTreeClose
    else
      NERDTreeFind
    endif
  else
    NERDTree
  endif
endfunction

" open NERDTree with ctrl + n
nmap <C-n> :call ToggleTree()<CR>

To go along with Chen Rushan's post, the

autocmd BufEnter * call SyncTree()

won't let NERDTree close. I couldn't find a solution (other than below) that would highlight the current open buffer in NERDTree while allowing NERDTree to Toggle.

Below is what I scraped together to be able to toggle NERDTree and have files highlighted while using Ctrl + ] for my next buffer mapping.

Hopefully others can improve this.

"Buffers
set hidden

function! IsNERDTreeOpen()        
  return exists("t:NERDTreeBufName") && (bufwinnr(t:NERDTreeBufName) != -1)
endfunction

function! NextBuffer()
     bnext
  if IsNERDTreeOpen() 
       NERDTreeFind
       wincmd p
  endif
endfunction

nnoremap <c-]> <Esc>:call NextBuffer()<CR>

function! PrevBuffer()
     bprev
  if IsNERDTreeOpen() 
       NERDTreeFind
       wincmd p
  endif
endfunction

nnoremap <c-[> <Esc>:call PrevBuffer()<CR>

function! ToggleNT()
    NERDTreeToggle
endfunction

map <c-u> <Esc>:call ToggleNT()<cr>

function! NerdTreeToggleFind()
    if exists("g:NERDTree") && g:NERDTree.IsOpen()
        NERDTreeClose
    elseif filereadable(expand('%'))
        NERDTreeFind
    else
        NERDTree
    endif
endfunction

nnoremap <C-n> :call NerdTreeToggleFind()<CR>