The Dynamic of Feelings in the Campaign
Feelings...hmm, this one is tough to handle for a few reasons. First, some players don't want to worry about that aspect (it doesn't make them comfortable and isn't fun). Second, you need a certain maturity level (not age level) to handle this properly. Finally, when the pieces are in place, you must take care to avoid derailing the campaign due to the consequences of certain feelings.
So, we will make the assumption that bringing feelings into the game (love, hate, friendships, enemies, etc.) can add an additional level of enjoyment for all of the players. I will now attempt to address the three reasons that I have defined above.
The first reason that feelings are hard to handle is that some players don't want to have this aspect added to thier game. For this player, you would want to identify why the player doesn't want this. If the player is uncomfortable dealing with emotional situations in a roleplaying environment, then an answer would be to bring emotions into the game very delicately. Focusing on fear and hatred would be a good start, as those are easier to roleplay naturally ("we run away", "we attack"). Once the player is more comfortable with his fears and hates, it will be easier to bridge those to the reasons for the fears and hates. Perhaps family and friends are pawns in an infernal game. The player hates and fears the demon prince because the demon is targeting those he cares about. You don't have to go that far, or place a PC's friends/families in danger, but involving them would help the player roleplay the relations. Love would be best left to the player to bring in, because it is a tricky emotion to deal with in game and an uncomfortable player may be scared away.
Another type of character that would not want to add feelings to their game may be used to computer based rpgs and wants to hack his way through your campaign as well. If the player is comfortable dealing with feelings in a roleplaying environment, then a solution may be to force the action. Utilize the character's friends and family in game. While in the tavern, the character's mother walks in and reprimands her son. Later, when something threatens the village, the player may thinks about the fact that his character has family here that should be protected. If the player is also uncomfortable, then use some of the advice in the previous paragraph to guide the player.
The second issue that may need to be dealt with is maturity level. This one is both simple and difficult. The simplest solution presents itself when the player makes it abundantly clear that maturity isn't something that he wants to deal with. For this player, I will touch on three options that are available. First, explain to the player what your goals are and that if he wants to play he should give some effort. Second, run the "feelings" aspect to the other players with the hopes that this player will adapt or at the very least not become a disruption. Third, part ways.
If the immature player is interested in this aspect, but doesn't know how, the solutions may be more difficult. The easy part has already been taken care of, because the player is willing to try. The hard part is that you are now put in a position of teaching someone maturity (this could be an adult or a child). The best method would be for the player to watch the actions of the other players and learn from their roleplaying. If that is not possible, you will need to mold the player. This may not be something that makes you comfortable (or is appropriate), so should be handled carefully. Utilizing NPCs as models of roleplaying will allow you to show how the player's character should react to situations (in the case of immature powergamers, you may go through a couple of NPCs before the player catches on

). As with the uncomfortable roleplayer, negative emotions will probably be easier to work with at first (and depending on the age of the player, may be the only appropriate emotions to deal with in depth).
Finally, now that you have players roleplaying with emotion (

), prepare for the campaign to be derailed. This is usually due to players roleplaying their characters' displeasure with another PC's actions. In order to keep the "realism" of the emotions, the players may be less likely to forgive and forget. In less emotional games, the party may make some crude comments at the offending member and move on in order to keep the game going. This can also happen with relationships that the party has with important NPCs that the part is meant to deal with. The best solution is to keep the campaign flexible and adapt it to the situations. You wanted to introduce these aspects to the game, so you must be willing to deal with the consequences. When it comes to intra-party strife, it may be best to take a time-out and hold an out of character meeting. Discuss options that would work for each player's character in order to keep the game going. Occasionally, the only option available will be for a player to start a new character.
So, when attempting to take a game to the next level emotionally, remember to keep a couple things in mind. Utilize care and other players to bring emotions into the game. Once you have your game of feelings, be prepared to deal with the issues that come with the territory.
I'll admit that this topic is not my "cup of tea", but it is still interesting to try to approach these subjects and try to add value...
Choice: Elements of Magic - Mythic Earth *if I was lucky enough to win yesterday, please reward someone else*