The Art of War has many things that apply to almost everything in life. Sure, you could go through each line and analyze how it applies to this game or that game, but IMO that's not the most effective way to utilize the book. Read through the book a few times and focus on different sections each time. If you want one that's the most impactful to RON IMO, though, it's I.18- "All warfare is based on deception." Simple and incredibly powerful. There are things you can't conceal (wonders, nukes, etc.) but using generals and ambush effectively, concealing where your main eco/mil buildings are, etc. can have major impacts on the game. Just my thoughts though.
If you're IT-savvy you probably know this already, but you could set up a VPN, have all your friends connect and play via LAN mode. This would be the way to go if you/your friends don't have and don't want to repurchase the Steam version. I hate that I own the RoN disk but needed to buy it on Steam anyway. I paid $5 during the Steam Winter Sale, and at $5 that's fair for "server dues" imo.
The VPN would have to be from a VPS or your home server. AirVPN, etc. wouldn't work. If you're not following, never mind lol
First off, are you both running the same operating system version, RON will not work if you do not have the same OP system and version of the game (although if you both got it off steam and are playing the “extended edition” you should be fine because some of those early bugs have been worked out). You could try direct IP connection there should be a button for that in the menu where you join a game. You could try using hamachi to set-up a local game that way, it will function as if your on the same network. Link: https://www.vpn.net/
I do not use steam, I have the game I bought a long time ago and I play with my friend who lives in Canada and hamachi works very well.
More stuff I found on steam for troubleshooting: https://steamcommunity.com/app/287450/discussions/1/46476691937004568/
Did your friend create the game first, otherwise it will not show up. Did you both make exceptions in the firewall for the game? Again, it will not work if these exceptions have not been made.
I used to use Himachi all the time, but now I use Evolve. You should really think about getting it, though. It's $8 on Amazon, or you can wait for a Steam deal on it, which happens rather frequently for about the same or less.
Put it this way: The more the HD version sells, the more likely chances are someone will greenlight making a true sequel.