How to secure LANs from one another as if they were the public Internet

RouterOS General
1

I have 3 separate LANs sharing a single Mikrotik firewall NAT. Anyone knows of a good article on how to secure each LAN (i.e. firewall, NAT) from the other two and the Internet? Thank you!

2

http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1

3

Wow, I had read about VLAN and it always seemed so complicated but the link you sent brought the concept to a level that I actually made sense. I was kind of wishing to keep the Mikrotik configuration as simple as possible but now I see that I may have to configure each of the three ports into a VLAN and use rules to prevent inter-LAN access. Next step will be to figure out the configurations files in the examples give. Thank you!