promises.js

//callbacks
$http.get(somepath, function(res, err) {
  $http.get(somepathother, function(res2, err2) {
    $http.get(somepathotherother, function(res3, err3) {
      //dostuff
    });
  });
});

//promises
var promises = [];
promises.push($http.get(somepath), $http.get(somepathother),$http.get(somepathotherotehr));
$q.all(promises).then(function(resp) {
  var res = resp[0],
      res2 = resp[1],
      res3 = resp[2];
  //do stuff
});

//sequentially
function get1() {
  return $http.get(somepath).then(function() {
    //do stuff
  });
}
function get2() {
  return $http.get(somepathother).then(function() {
    //do stuff
  });
}
function get3() {
  return $http.get(somepathotherother).then(function() {
    //do stuff
  });
}
//callthem
get1().then(get2).then(get3);

//still possible to christmas tree ;)
$http.get(somepath).then(function() {
  //do stuff
  $http.get(somepathother).then(function() {
    //do stuff
    $http.get(somepathotherother).then(function() {
      //do stuff
    });
  });
});