Teach your dog to be happy about giving up objects to you first using information from ‘How To Get The Toy Back After Play’.  If you want your dog to give toys or objects direct to your hand, train this well first.

To teach your dog to drop things on cue, ask him to fetch a toy or object that isn’t very valuable to him, then, when he brings it to you, say ‘Drop’ and give a hand signal (e.g. point to the floor), then hold something much more valuable, such as a tasty treat, high above him.  Wait until he drops the toy or object, then feed the treat and reward him well with praise. 

Repeat until he understands the cue (either the hand signal or the word itself - words are more difficult to learn) and will ‘drop’ what he is carrying in expectation of a reward, even though the reward is out of sight.  Reward him well for dropping and he will do it for you every time.