1.  Infinite Credits

The following trick only works between the two indicated vendors. You can usually buy items back from Expat at half the price you sold them to Dr. Michel for. First, successfully complete the side quest involving Dr. Michel (from the Med Clinic) and her blackmailer. After the quest is complete, you will get a discount from all the goods she sells. Start selling her all of your expensive equipment. Then, travel to the Wards Markets, and talk to the merchant named Expat. You can buy all of your items back for cheaper than you sold them for. Return to Dr. Michel, and sell her all of your items again. Repeat this process as many times as desired.

2.  Infinite Paragon Points

Go to your Galaxy Map, and travel to the Attican Beta cluster. You will receive a message from the Alliance Command telling you about a downed recon probe that you must retrieve a data module from. From there, travel to the Hercules system, and continue to the planet Eletania. After you reach the downed probe, you will discover that a monkey-like native has made off with the data module. Get back in the Mako, and go to your map. You will see three native colonies. Go towards the one in the middle of the three. Then, go into the mining shaft, and proceed through the tunnels until you reach the end. Search the two monkeys in that part of the shaft. One of them will have the data module. Save the game immediately after getting the module. Then, reload the saved game, and continue to press A to keep searching the monkey that had the data module. Your Paragon meter over the radar should increase each time you select the monkey. At approximately 300 Paragon, you will get the "Paragon" achievement. Note: If you have already completed this assignment, this glitch cannot be done.

On the Noveria planet, go to the hotel bar, and look for a Turian named Lorik Qui’in. Accept his quest to steal the data from his office. Once you get the data, the receptionist will ask you to get Qui’in to testify. Tell her you will do it, and then talk to Qui’in. Tell Qui’in that he should testify (top left option). When he refuses, select the Charm option (top left) for Paragon points or the Intimidate (bottom left) for Renegade points, and end the conversation. Talk to him again, and ask about the Matriarch. When he gets done talking about her, select the "Other questions" option (bottom right). You should now have the option to ask him to testify again (top left). He will refuse, and you will be able to use the Charm or Intimidate option again to gain another 24 Paragon or Renegade points. Repeat this process as many times as desired. You can also easily get the "Paragon" and "Renegade" achievements with the glitch.

To gain extra experience from battles, make sure to get out of the Mako for the final hit. You can weaken the stronger enemies from inside the Mako and then get out to finish them off. You will only get 60% of the experience if you kill enemies with the Mako.

If your Mako is badly damaged and you do not want to or cannot spend Omni-gel to repair it, save your game, and reload it. Your Mako should now be totally repaired.

Get a HMWA X assault rifle with Frictionless Materials, Combat Optics X, and Snowblind Rounds X as upgrades.

If you are a Soldier, level up weapons so you can use their bonuses and no further. For example, carnage is the shotgun’s bonus. By doing this, you will have extra points for a desired weapon and points to level everything else completely out. You do not need the damage and accuracy bonus from the points because when you become a Spectre the best of every weapon becomes unlocked in the Normandy or at the C-SEC requisitions office.

Equip any good sniper rifle (powerful and accurate) with High Explosive Rounds (highest level preferably). This combination will kill nearly every normal enemy it directly hits, and severely damage enemies in their proximity, if not killing them as well. For fun, if you shoot at the enemy’s feet or the ground he is standing directly on top of, he will jettison into the air. NOTE:  High Explosive Rounds work best only with sniper rifles as they are meant to kill with one shot. If it is used with a pistol, assault rifle, or shotgun, the weapon will overheat in less than five shots (depending on the type of weapon), regardless of upgrades and decency of the gun. This will make yourself vulnerable to enemies.

Successfully complete the indicated task to unlock the corresponding bonus the next time a new game is started. Once the game is completed, the "New Game +" option is also unlocked, which allows you to use your existing character with previously earned equipment and skills.