I am starting to think of including sounds in my mod.

Which class should I use to play sound?

Or,is there a "manager" thingee that is required to play sounds?

[lmgtfy=minecraft forge sounds]Google is your friend.[/lmgtfy]

you just need to create sounds.json UTF-8 file like this:

{
   "fire": {"category": "master","sounds": [{"name": "chinesegun/fire","stream": false}]},
   "reload": {"category": "master","sounds": [{"name": "chinesegun/reload","stream": false}]},
   "empty": {"category": "master","sounds": [{"name": "chinesegun/empty","stream": false}]}
}

then simply place it to "minecraft\modding\forge-1.7\src\main\resources\assets\<your mod name>\" folder.

then simply use world.playSoundAtEntity(player, ModId + ":fire", 1.0f, 1.0f);

you don't need to register your sounds, just play it.

After you create your sounds.json file in your project, play your sound however you please. For EG:

public void test(EntityPlayer par1EntityPlayer, World par2World)
{
    par2World.playSoundAtEntity(par1EntityPlayer, "SOUNDNAME", 1.0F, 1.0F);
}