What is the usual way to select an online game ?
Usually people will host open games, typicallying calling it "5v5" or something to that effect. Join whatever game looks good to you.
to get the password ?
You ask for it. Join the chat channel of the game in question (it's the same as the game's name) and request the password. If there's a password, that tends to imply the game is somewhat exclusive, so if you're new and have no one to vouch for you, you probably won't be let in.
to select game conditions (speed , ...) ?
Games online are almost always played with all-fast settings, no pirates, normal fleets, and quickstart.
Is there a forum that post game in advance ?
Nope, people just make games and join what is available.
