Update: I was unfortunately not aware of Shamus Young's severe criticism of Fallout 3 available here to link in the original piece and I regret that. It dovetails rather nicely with what I've written and it's much better executed than my piece. I strongly recommend anyone...
In order to do this glitch you need to do a mission that you don't have any cutscene to go through, including at the completion. An example is the mission called "Map of Occupied Kirkwall". When you have gotten all of the objectives done other than giving the item to the person, you go to the person with your weapon drawn, and while your weapon is still drawn and you are right in front of the person, you repeatedly press the A button. You will get money and exp repeatedly as you press the A button. The exp is limited to a maximum of when all your characters are level 50 however so be careful how you spend the ability and charater points. The gold though you can do as long as you wish, but when you stop pushing the A button past the mission speech you can't do it again with that mission.
Unlimited ability points.
To activating this glitch requires that you access the black emporium and purchase the potion "Makers Sigh" which will reset all of your ability points and attributes. Hawke comes preloaded with preset skills he/she is "supposed" to have. Meaning when you use a makers sigh and save, those abilities will be filled once you re-load. Here are the steps to using this glitch:
1. Use makers sigh
2. Save your game.
3. Load your game
4. Check your ability points because you should have the amount that were taken away, plus the ability's that Hawke is "supposed" to have. For a rogue it will be around four - five points in the dual wield tree (5) If you use another makers sigh, it will now add those ability's to the ability points available. You must save and reload each time you wish to do this again.
Infinite XP and Gold Glitch
Before finishing a side quest that doesn't trigger a cutscene, draw your weapon. Once your weapon is drawn, talk to the NPC that completes the quest. Once your character puts his or her weapon away, repeatedly hit A till desired level or gold amount is reached.
Infinite points in Armor
This can be done with Aveline or Warrior Hawke at any point in the game. All you have to do is equip, un-equip, and then re-equip a shield. Do it as many times as you want till you max it out.
Item Dupe and Money
Place your most expensive item into your trash alone. Go to a merchant, select sell and go to the trash tab. Hit Y and immediately press A. If you were successful the item you sold will have sold twice giving you extra money. To duplicate potions you must purchase two or more than do the above cheat. Enter into buy mode and buy back all but one of the item you wish to duplicate. Repeat the cheat and your stackable item should have increased for as many as you have sold.
A Friend in Need (5)
Upgraded the armor of one of your party members.
A Worthy Rival (25)
Earned the Arishok's respect.
Arcane Defender (25)
Sided with the mages five times.
During each year in Kirkwall, discovered 3 secret messages from the Band of Three.
Kicked the slavers out of your ancestral mansion.
Champion of Kirkwall (20)
Completed Dragon Age II.
Chantry Historian (25)
Found all four chapters of "The History of the Chantry," by Brother Genitivi.
Defeated Meredith, knight-commander of Kirkwall's templars.
Acquired your first crafting recipe.
Crowning Glory (25)
Became the viscount of Kirkwall.
Darkness Falls (5)
Toggled the map from day to night.
Reached Level 10.
Delver of the Deep (10)
Explored the Deep Roads.
Demon Slayer (25)
Found and killed the ancient demon, Hybris.
Dragon Slayer (25)
Found and killed a high dragon.
Enchanted an item.
Completed Dragon Age II twice, or completed it once with a save imported from Dragon Age Origins.
Found and killed the undying Xebenkeck.
Left Kirkwall to explore the outlying regions.
Became a partner in a Deep Roads expedition.
Flirted with one of your party members to begin a romance.
Earned the friendship of one of your party members.
Friends in High Places (15)
Met Grand Cleric Elthina, Viscount Dumar, Knight-Commander Meredith, and First Enchanter Orsino.
Full House (10)
Recruited four party members.
Gift Giver (5)
Gave a gift to one of your party members.
Great Minds Think Alike (50)
Earned the friendship or rivalry of four party members.
I Got Your Back (25)
Completely upgraded the armor of one of your party members.
Became a resident of Kirkwall.
King of the Hill (10)
Defeated the Arishok.
Unlocked 100 codex entries.
Reached Level 20.
Mage Hunter (25)
Sided with the templars five times.
Mass Exodus (25)
Reached Kirkwall with each character class across multiple playthroughs.
Master Craftsman (25)
Crafted all of the items from a single crafting tree.
Allied yourself with the mercenaries upon arriving in Kirkwall.
Had 100 or more sovereigns in your purse.
Allied yourself with the smugglers upon arriving in Kirkwall.
Earned the rivalry of one of your party members.
Completed a romance with one of your party members.
Learned two class specializations.
Visited 10 caves in Kirkwall and the surrounding area.
Stone Cold (5)
Defeated the rock wraith on your expedition into the Deep Roads.
Found every variety of crafting resources.
Tag Team (5)
Used teamwork to perform a cross-class combo.
Tale Within a Tale (5)
Listened to Varric begin his tale of the Champion of Kirkwall.
Upgraded a spell or talent.
That Thing Has Legs (25)
Found and killed a varterral.
Treasure Hunter (25)
Opened 50 chests.
Completed a full year in Kirkwall without any party member being knocked unconscious.
Weapon Master (25)
Mastered a weapon style.
Achievements: Legacy DLC
Defeat an ancient evil in the Vimmark Mountains.
Deep Roads Safari (15)
Kill a genlock, genlock alpha, hurlock alpha, bronto, and deepstalker in the Vimmark Mountains.
Family Legacy (30)
Apply three effects to Hawke's Key.
Family Outing (15)
Complete the main quest in the Vimmark Mountains with Bethany or Carver in the party.
Tower Sweeper (30)
Complete every side quest in the Vimmark Mountains prison tower.