You should always be able to run local for your current directory version of ANGULAR CLI by running:

node_modules/.bin/ng <ANY NG COMMAND>

instead of just

ng <ANY NG COMMAND>

just make sure, you are running this command from the root directory where your main package.json is located (and its node_modules directory)

There is an npm command returning node_modules/.bin path (which may be used for shorter writing):

// does not work on Windows   
`npm bin`/ng <ANY NG COMMAND>

Note that back ticks are used around npm bin and not single quote sign.

ng command is also added to package.json scripts section, so it is also possible to run local copy like this:

npm run ng -- <NG_OPTIONS>

note -- flag terminator, it must be inserted before ng options.

If you want to create a new ng project using particular version but without installing @angular/cli globally, you can use npx command:

npx @angular/cli@7 new <APP_NAME>

here npx will temporary install @angular/cli with latest (@7 at the time of answering :)) version and run its ng executable with passed parameters.

You even can do something completely useless (because local copy of @angular/cli was installed with ng new). Run ng serve with @6 version of CLI on @7 new project:

cd <APP_NAME>
npx @angular/cli@6 serve

UPDATE

Running these commands will use ng executable located locally within node_modules/.bin/, so you do not need to have it installed globally:

cd <APP_NAME>
npx ng serve

In case someone else came here like me with the same problem, I found this method as the easiest. I had @angular/cli@1.7.3 installed globally as I have an ongoing project created from that version(angular 5.0 roughly) but wanted to install @angular/cli@6.0.0. What I did was installing npx and then created the project using npx

Install npx frpm npm

npm install -g npx

Create new project with the desired cli version. Use @angular/cli@latest or just @angular/cli for the latest version.

npx -p @angular/cli@6.0.0 ng new my-project

Inside the project root folder, execute ng --version to see the version of you cli. But I recommend you use npx prefix to every command that uses ng as follows.

npx ng --version

npx ng generate component my-component

Here the npx look for the ng command exists locally in ./node_modules/.bin/ directory and executes it.

You could use NVM which is a Node Version Manager and allows you to work with different global modules in each Node version.

In my case, I'm working with Node 6.9.5 and Angular2 in one project, and Node 10 and Angular6 in other.

You only have to pay attention which version is seated and work as normally as you do.