I switch between enough different projects with different coding styles that I have shortcuts to change between them:

    set expandtab
    set shiftwidth=4
    set softtabstop=4
    function Spaces(...)
        if a:0 == 1
            let l:width = a:1
        else
            let l:width = 4
        endif
        setlocal expandtab
        let &l:shiftwidth = l:width
        let &l:softtabstop = l:width
    endfunction
    command! T setlocal noexpandtab shiftwidth=8 softtabstop=0
    command! -nargs=? S call Spaces(<args>)
    autocmd BufNewFile,BufRead ~/src/linux/* T
    autocmd BufNewFile,BufRead ~/src/git/* T
    autocmd FileType html S 2
    autocmd FileType tex S 2

This sets the default to 4-space indents, but lets me do :T to switch to tabs (and does so automatically for Linux and Git which use that style), or :S N to switch to N-space indents (and automatically switches HTML and TeX to 2-space indents).

I use vim-sleuth to auto-detect indentation settings.

https://github.com/tpope/vim-sleuth

Thanks, I've edited the post to mention about putting everything in one lien.

Why nocompatible?

Not necessary, AFAIK, unless you invoke vim using the alias "vi". If you call "vim" it'll start in nocompatibe mode by default.

The nocompatible mode means adding some features to vim rendering it "incompatible" with the original vi. For example in the original vi you can only undo the last action, with compatible mode on vim will mimic this behavior.

Takes a whole stroke off your shell game!