Very often I find myself tired needing to manually refresh my browser after every little change I do to my code. It is not too hard to do it, but sometimes it is just so annoying.
In such cases I like setting up Rails app preview auto re-loadable. It's pretty easy to do and only takes 5 steps:

First off, let's install a couple of gems into development environment, since live-reloading doesn't even make sense on production.

STEP 1: Add the following to your Gemfile:

gem 'guard-livereload'
gem 'rack-livereload'

and run 'bundle install'.

Alternatively, you can run these commands from within your terminal to install the necessary gems

bundle add 'guard-livereload'
bundle add 'rack-livereload'

STEP 2: Next, we need to initialize livereload, by running:

bundle exec guard init livereload

STEP 3: Now add the following line to the very end of file enviroments/development.rb

config.middleware.insert_after ActionDispatch::Static, Rack::LiveReload

STEP 4: Now you can run the command to start the livereload guard. Keep it running alongside your puma server.

bundle exec guard

PS. You may need to restart your Puma server before livereloading starts working.

STEP 5: install 'LiveReload' extension on your browser.

In order to start your autoreloading preview do this:
start your Puma Server

rails start

start your autoreload guard

bundle exec guard

Make sure to do so in the browser with LiveReload extension running.

That's pretty much it. Now every time you save your code-base file it'll auto reload your browser tab.

You may also watch the video about it on my YouTube channel: