Please don't flame me--If you don't like the exploit, then don't use it.
When you get to the town of Ostagar and decide to continue the main quest, you approach Duncan with Alistair. After speaking with Duncan, he gives you a quest which is really your initiation into the Grey Wardens and must be completed in order to advance the game. Alistair, 2 other Grey Warden applicants and your character are then sent into the Kokari Wilds to a) obtain 3 vials of darkspawn blood for your initiation rite into the Grey Wardens and b) to obtain Grey Warden scolls that Duncan wants that are treaties pledging support for the order. Ok so far? Good. It's probably a good idea to save here and when you come back so if there are any problems you don't have to restart the game from the origin story if you haven't done so already or if you have autosave turned off.
Now take your party and go out into the Kokari Wilds. Kill some darkspawn so that you can fill the vials with blood. Do NOT do the scroll quest yet! (It's probably a good idea to a) complete the prisoner quest in Ostagar before you leave Ostagar and b) obtain the Mubari Hound quest so you can get the flower at the same time you kill your first set of darkspawn. This will allow you to complete both quests before talking to Duncan)
Now once you've completed both quests if you are going to do them AND have the 3 vials of darkspawn blood, talk to Duncan. (Again, it's a good idea to save your game just BEFORE you talk to Duncan so that if you make a mistake in leveling up or don't like the choices you've made, you have a place to reload from)
When you talk to Duncan, he will ask if you've completed the quests he has given you. Respond by saying that you have the vials of Darkspawn blood. Duncan will then ask if you have the scrolls. Alistair interrupts and says basically no. Duncan then tells you to get it done. This then ceases the conversation and you can control your party again.
What's important is that you are AWARDED 750 experience points for completing the vials portion of the mission while leaving the scolls quest still open. (These are two seperate quests in your journal even though they are linked) This allows you to save and TALK TO DUNCAN again. The same conversation loop occurs. Each time you do this, you get awarded 750 experience points. (The experience points may be more if you are wearing gear that increase exp earned, like the Formari Memory Band. I was, for example, getting 757 experience points) This ceases once you bring back the scrolls.
This will allow Alistair and your character (not the other two party clowns who are only in your party for these 2 quests) to level up an unlimited number of times. I don't know if there is a cap or not as I haven't had a chance to experiment with the extremes yet. I do know that you won't get specializations until you have unlocked them by finding a trainer or book. You DO have the specialization points saved so that when you do unlock your specializations, you can chose and advance their chains. These specialization points are obtained at levels 7 & 14. (I don't know if you can get another at level 21, etc or if specializations are capped at 2 only) It might be a good idea to save some talent points to put into your specialization chains later on.
I don't know if this will break your other party members when you get them since they level up based on your level. Again, be warned.
As far as I have experienced, this does not break the main quest or the game.
Enjoy!
