well you need to make sure that if you are behind a firewall that your firewall isn't blocking other people from seeing your server.  also the ip you give people should be your outside ip, not your internal one.

Yeah its also best if you have a dedicated ip address (doesn't change from month to month or every time you turn on your pc) and that your isp or router isn't blocking your hl2 gameport 27015 to 27025 +  as it can be hard to figure out how to open these ports if you don't know how too and and everyone’s router can be different.

And the biggest pain can be only seeing 192.168.1..... Don’t give someone this ip to connect to as this is your internal network ip and no one will be able to connect to your pc using that ip.

But with so many members one of you should have no problem to get a server setup.

Here is a little info about hl2dm servers  - most still applies to hl2ctf servers

Starting your own server

Configure the connection

To start your own server, there are some things you first need to do to get your server ready.

1. Make sure you have port 27015 open on your router. Go into your router's configuration, and enable port forwarding for port 27015 to go to your PC in your LAN.

2. Make sure you have all traffic for port 27015 allowed if you have a software based firewall on your PC. Set up a rule in your firewall to allow traffic from this port, or simply turn off your firewall while you are playing the game.

3. Enable the console in Half-Life. There are two ways of doing this. The first way is to find the shortcut for HL2, or HL2DM, right-click it, and select Properties. In the target box, after the xxx.exe file, type a space and -console. The second way, and probably the better way is to open up steam, right-click the game in the My Games list, go to Properties, and click Launch Options. Type the -console in there and Save. Now with the console enabled, you can press ~ during the game to bring the drop-down console into screen to type in some extra features.

Starting the game
With that all set up, now it's time to start your game. Simply run HL2DM.
When you get to the main screen, you will see another window in there as well, that is the console you enabled. You can always close the console if you wish, and reopen it with the ~ key.

There are some commands you need to type in the console to ensure that it will allow other people to play on your server.

net_start (enables internet play)
sv_lan 0 (disables lan play)
deathmatch 1 (enables deathmatch play)
maxplayers 5 (sets the maxplayers, any number up to 32)

Also on wall jumping I learned pretty quick on 2fort by using the back wall on top of the battlements to wall jump and you have plenty of room once you land on the roof of the snipers nest to jump off the other side and repeat as much as you like in the opposite direction until you can do it in your sleep.

Also it really helps if you reconfigure your mouse wheel up key to jump..... You will pick it up much faster.

Same goes for bunny hopping / strafe bunny hopping.