If you're having issues with your local instance, these two methods are your best bet.
If you're having 500 errors any of the app's URLs, try the following.
Enable debug mode by editing the .env file and replacing APP_DEBUG=false with APP_DEBUG=true. This will now show the error in the browser, which can give you a hint as to what went wrong.
If you want access to the detailed error logs, execute the following commands.
tail -f storage/logs/laravel-{date}.log