Tips:

Missions:

Start Playing on Solo Secret Agent to earn both Agent and Secret Agent Achievement. After this it's better to start Co-Op Perfect Agent with a friend. After completing this you'll be able to play Dark Agent Solo and Co-Op. Start playing Solo on Dark Agent because you'll recieve the Perfect Agent too. The One and Five Mission on Dark Agent are easy to earn because Six of the Missions are easy to complete on both Solo and Co-Op. For example, Mission 00, 01, 02, 05, 10 and 12. You can find some useful Video Walkthroughs on http://pdzvideowalkthroughs.blogspot.com/

DeathMatch Games:

An easy way to receive these Achievements is:

- Team Killcount

•  Urban
•  Small
•  5 Kills
•  15 Dark Bots
•  Only RCP 90s
•  Put 7 Bots on your Team and 8 on the opposite Team.

Start the game and wait for one minute. The Dark Bots should have killed 5 enemies within a minute.

DarkOps Games:

You’ll gain these Achievements after the Infection Kills and Rounds Survived Achievements. If you don’t, just start some one round Eradication and do the same as I told by the Rounds Survived tips.

Melee Kills:

Start a Killcount Game against Agent Bots with Viblades only. It would take you only an hour to get 1000 Melee Kills. But beware, kills from behind doesn't count towards these Achievements!

Explosive Kills:

Start a Team Killcount team against a lot of Agent Bots on urban with Mines only. Run towards their base and keep throwing mines in their base entrance. You should have 100 Explosive kills within 30 minutes.

Headshot and Sniper Kills:

The easiest way to get these is using a second controller and just play Killcount. Just keep shooting the second controller in his head with the sniper. If you don't have a second controller you can do the same with Agent Bots on Desert but it'll be a bit harder.

Rounds Survived:

#1
Best way to receive this Achievement is by playing with 10 Dark Agent bots against 1 Dark Agent bot. It shouldn’t take more than 30 seconds before they kill him.

#2
These Achievements are also easy by using a second controller with these settings:

•  Eradication
•  Old Town
•  Base 2 and 4 Open
•  5 Rounds Limit
•  A strong starting weapon

As soon as you spawn run towards the enemy base and kill the second controller. Do this for 5 times and you'll finished a DarkOps Game. You should receive the 1000 Rounds Survived Achievement after 200 DarkOps Games played. It might be smart to make 2 extra accounts, so you'll know when you played 100 Games because the other account will earn this Achievement too. Use the other account after this happened.

Property Destroyed:

Play with a friend or a second controller to gain these Achievements fast. Start playing and destroy every Property from your opponent. Destroying every Property in one Round should be 10K Credits. You can blow these Properties by Grenades, Mines, Rockets or Demo Kit or just shoot them.

Minutes Survived:

Same as the Property Destroyed Achievements, this one is also easy by using a second controller or playing with a friend. Just set a long time limit and just wait till the rounds finished. If you play with a second controller you can kill it.

Flag Captures and Territorial Gains:

You can start these Games without enemies so it'll be very easy to capture and gain enough points.

Infection Kills:

Best way to get this Achievement is by using a lot of Agent bots. Start with 15000 Cr. And buy a Plasma Gun, start killing your team mates, this also counts towards Infection kills. You should be able to get about 5-6 team kills a game.

And finishing a Game is necessary to get the score of that game towards your Achievements!