What should I look for in Command prompt when I'm looking for an available IP???

What should I look for in Command prompt when I'm looking for an available IP, when I type "ping xxx.xxx.xx.xxx"?

Also what should I type for the x's, if my PC's ip address is "192.168.2.12"?

normally you change the last octet of the IP address until ping finds no response,

ping 192.168.1.13 ping 192.168.1.14 ping 192.168.1.15 etc

But fortunately there are free programs that can do this for you e.g. - http://www.radmin.com/download/utilities.php -

You need to be a little cautious, because an address that is free today may not be free in an hour's time. I assume you are using some sort of router on an internal network, judging by your IP address. If you just choose "one up" from the last one in use, the next time the router needs to allocate an address, it may choose that one, then you have major problems.

The private IP address range starting with 192.168.x.x goes from 192.168.0.0 – 192.168.255.255

The best thing would be to check whatever it is that allocates the DHCP addresses (probably your router) and look at its configuration. There is normally an IP address that you connect your web browser to, to achieve this.

Then look for something like this (from my router):

In my case I am using the private IP range starting with 10.x.x.x, and you can see from the graphic that the DHCP server is configured to allocate addresses from 10.0.0.101, with a maximum of 50 (so the highest would be 10.0.0.150).

So in my case, I could allocate 10.0.0.160 (say) for a statically-allocated device, like an Arduino, without any possible future problems. Of course, that assumes that I don't forget, and allocate 10.0.0.160 next month to a different gadget. So some sort of manual documentation might be advisable.

In command prompt simply write “ipconfig/all” , you’ll get your ethernet ip address like 192.168.1.100 so add 1 to its last digit i-e 192.168.1.101 and write “ping 192.168.1.101” if it gives you ‘Request time out’ and 100% loss so this ip is free for your use, if not so then again add 1 to the last digit of your ip and repeat the process.

Thanks! That is very helpful!

Instead of ping you might want to try nmap. Anyway you should listen to Nick Gammon's advice.