Step 8 - Security is important
Powering up a PC remotely, opening ports on your firewall, enabling remote login, and enabling ping capabilities all expose your PCs and network to the world. It's up to you how you manage that risk. For example, you can turn off ping capability on your router and disable your port forwarding rules. If you have enabled remote login to your router, you can then turn on the ping and forwarding rules when you need to power up a PC, and turn them off when you don't.
Regardless of OS, you need to set up the PC you subject to WOL to require a username and password for remote login. Windows Remote Desktop Connection is a useful way to remotely access a PC, and should be set up with a username and password. VNC software should always be configured to require a password on remote login.
Use secure passwords. Change the passwords on your router and PCs to unique, 8 or more character mixtures of uppercase and lowercase alphanumeric characters.
Test it at home before you leave your house with your PC off, hoping to turn it on remotely. Then, test it remotely with someone else at home to turn on your PC if WOL isn't working.
When all is said and done, you'll have a pretty cool solution: the ability to remotely fire up your PC with a keyboard from anywhere on the Internet. Plus, you'll save money and electricity by leaving your PC off when you don't need it.