Bukkit

private SimpleClans sc;

public void onEnable()
{
    Plugin plug = getServer().getPluginManager().getPlugin("SimpleClans");

    if (plug != null)
    {
        sc = ((SimpleClans) plug);
    }
}

public void doClanStuff()
{
    // get a player's clan

    if (sc != null)
    {
        ClanPlayer cp = sc.getClanManager().getClanPlayer("Phaed");

        if (cp != null)
        {
            Clan clan = cp.getClan();
        }
        else
        {
            // player is not in a clan
        }
    }

    // get a clan from a clan tag

    if (sc != null)
    {
        Clan clan = sc.getClanManager().getClan("staff");

        if (clan != null)
        {
            // clan exists
        }
    }
}