Basically, you go to the menu, you go to where it says "Addons", then you hover your cursor over the mod you want, then you click install, after all that, you go to the spawn menu by pressing "c" on your keyboard when you play by yourself in single player, then go to Addons in spawnlists, then click a group, then click a picture or model, then it will appear. Some various mods can cause lag though. Also another way to download mods is through the steam workshop all you have to do is open steam go to your library go in Garry's Mod go down to the workshop area and download I prefer go do it this way because most mods require for you to reboot Garry's mod
no because garrys mod requires that you have a game that uses the source engine
you cant unless you download an add on (http://www.garrysmod.org/downloads/?a=view&id=46486)
No. Unless it's a glitch, the only way you can spawn them other then mods or console is going into the NPCs section and manually spawning a zombie.
It depends on what the player does i guess But its mostly what Half Life 2 is rated If the player has counterstrike source also installed the content (Characters and guns) gets transferred to garrys mod so they can play around with it in the game, it depends on a few factors (1) what will they do? (2) what other games that rely on the source engine do they have installed? (3) what do you think is suitable for them in garrys mod, they are only limited by their imagination, in Garrys Mod you can build pretty much anything, and i mean anything
Garry's Mod doesn't have its own sound effects and stuff, so you have to add them. I've been trying to find a way how to add my own sound effects to Garry's Mod, but I haven't found out a way yet.
for that you probably will have to buy?/rent a server. you can get one at the related links below.
Buy Garry's mod 10 off of steam.
technically yes, there were a few updates it is still called Garrys mod 10 though
Garry's Mod 10
no because garrys mod requires that you have a game that uses the source engine
Garry's Mod has now updated and includes all features of 13 Beta
Garry's mod tornado
Yes. Optifine can count as a mod. Just place your optifine.jar in the mods folder, and add other mods with it.
Steam
yes
you cant unless you download an add on (http://www.garrysmod.org/downloads/?a=view&id=46486)
You Do Not Get Garrys Mod Serials, You Buy it Off Of Steam Which can be found at steampowered.com its usually about 21 United States Dollars