Which levels contain achievement pickups

This problem has different solutions depending on how you want to play.

If you're just looking for the achievement, one solution to your problem is to do whatever missions you want, choosing the side of good, until you get relatively close to your level point. Then go into a town and steal (for minor karmic reduction) or lay waste to entire towns (for major karmic reduction). You can quickly lower your karma this way. Then, once you're neutral, go kill some random creatures until you level.

(If you're looking to steal, a good place to do it is at Dukov's place… he's got stuff everywhere.)

The "nice" thing about this system is that if you stay on the path of "good" the whole time, you can do this at each achievement point: be bad until you get to the right karmic level, level up, get your achievement, and then restore a save to get back to your good self. You can quickly get "good", "neutral", and "evil" achievements for all levels on one playthrough this way.

(I did this, because I don't really enjoy long-term playing as an evil character… but I do like my achievements!)

You could also do this as an evil or neutral character, but it's much easier to quickly drop from "good" down to your new goal, than to work your way up.

If you find that you're close to leveling, and you're at the right karmic level, and don't want to take a chance on changing your Karma by doing a story-type adventure, you can always go wandering looking for random bad people to take out. Going near the Washington Mall can get you some XP fairly quickly, and you can go inside the capitol building and clear out large areas without picking up any Karma, positive or negative.

Looking at that list of multiplayer achievements and based on my own personal experience online, the majority of them will be very easy to get through regular play. Here's some tips on getting some of the trickier ones.

Mastering the Art:

Earn the INCOGNITO bonus (Multiplayer).

You need to get an incognito kill. Depending on your skill level, this could be a tough one to get. To get an incognito kill, you must fill up your approach meter to the max by keeping your target within your line of sight without running up to it or otherwise making yourself noticeable. Note that you can run without reducing the meter if they are not within your line of sight.

Make the Headlines/Tactician:

Obtain 12 different Accolades (Multiplayer).

Score at least 2500 points in a session (Multiplayer).

To be successful in multiplayer, you need to always go for the quality kills. You won't necessarily win by getting the most kills, you win by getting the most points and kills only grant you 100 points. If you are more patient, you can get bonuses to earn you even more points. Being fast an efficient will get you this achievement naturally.

This could be tough getting because you will need to be quick at getting your quality kills while still fending off pursuers. I can't really help much with this, you just gotta be a machine and some other players can be very difficult to beat. Though out of all the game types, Deathmatch might be the easiest to get it in as everyone is in a confined space and there aren't (normally) any lookalikes so should be easier to find your targets.

The other achievements you should be able to naturally earn if you go after the True Templar achievement of level 20. Depending on your skill, it might take a couple of days or so of playing. You shouldn't strain yourself over this too much if you plan on playing a lot.