PaquitoSoft

var step = 0;

async.waterfall([
    function (next){
        step = 1;
        getJson('/user', function(user) { next(null, user); });
    },
    function (user, next){
        step = 2;
        getJson('/twitter_profile', user.twitterId, function(twitterProfile) { next(null, user, twitterProfile); });

PaquitoSoft

var step = 0;

async.series([
    function (next){
        step = 1;
        getJson('/country', function(data) { next(null, data); });
    },
    function (country, next){
        step = 2;
        getJson('/weather', function(data) { next(null, data); });