First, install PuppetDB on your puppetmaster, as it will greatly make Puppet administration easier.

After that, you can check for nodes which are registered by puppet, by using command:

curl -s http://localhost:8080/v3/nodes

To query inventory for nodes:

curl -k -H "Accept: yaml" https://localhost:8140/producton/facts/*

To de-activate node:

puppet node deactivate NODE_NAME

To find out what's puppet master certificate name (very useful in troubleshooting DNS related issues):

puppet master --configprint certname

To check if there are any puppet client nodes waiting to be authorised on server:

puppet ca list

To sign puppet client requset:

puppet ca sign certname

To delete client certificate request:

puppet ca destroy certname