If you are doing clan challenges they are an easy way to get some Clan XP and some of the challenges are down right easy for good players. There are two types of challenges, one that you can do yourself and ones you need some team help or they are next to impossible.
Engineer - Most Bombs Planted: This one was a K/D killer since you have to fight to get a bomb planted and then hope no one else gets more plants. The problem is that you tie often with other players for the number of bomb plants and the game awards the accolade to only one of the tied player randomly. This challenge definitely benefits from using a team. Took me about 30 games to get 10 with two players.
Setting Up Shop - Most HQs Captured: This one really requires some teamwork. There are lots of teams playing this game mode and if you don’t have at least 3-4 team members to help then this one is very difficult to do solo. Took me about 28 games to get 10 with two players.
Tactician - Most Kills From Behind: This one is easy. Run Blind Eye, Assassin and Dead Silence and camp a popular pathway and let them run by and take them down from behind. Use of a portable radar is a plus. Took me about 14 games to complete this challenge.
On Target - Most ADS Kills:This one requires an optic on your weapon. Use a red dot sight and mow down the enemies while aiming down sight. Took me about 16 games to complete this challenge.
Dexterous - Most Throwing Knife Kills: This one is one of the easiest to get. Sometimes just one throwing knife kill got me the accolade. Took me about 11 games to complete this challenge.
Vigilante - Most Pistol Kills: One of the easiest to get. Just run around with dual .44 Magnums and get about 5 pistol kills per game and you should lock up this accolade. Took me about 13 games to complete this challenge.
Brazen - Most Hipfire Kills: One word for you… STRIKER. The striker is a hipfire killing machine. It has more more stopping power than when aiming down sight. Select the Damage or Range proficiency and its the best weapon for hipfire kills. Took me about 20 games to complete this challenge.
Far Out - Most Longshots: The best weapon for this challenge is the striker with the range proficiency on smaller maps. Its really easy to get some spray and pray longshots with the striker. I often get 5 or more in a row. I tried using a sniper rifle but you have to find reeeaallllyy looonnggg sight lines to cash those long shots so the striker can be used on any map with great effectiveness.Took me about 15 games to complete this challenge.
Efficiency - Most Headshots: The MK14 assault rifle is the best weapon for taking heads off. Took me about 20 games to complete this challenge.
Boom! - Highest Multikill: The RPG is good for multikills and running the predator missile and reaper are also good for multikills. Took me about 24 games to complete this challenge.
Top Shape - Most Specialist Killstreaks Earned: This one was pretty easy since few people run the specialist killstreaks. If you are good then getting this accolade won’t be difficult. Took me about 16 games to complete this challenge.
Flesh Wound - Most Knife Kills: Throwing knifes don’t count for this but the tactical knife does so consider equipping a pistol with a tactical knife and melee the enemies all game long. Took me about 18 games to complete this challenge.
Most of these challenges are easiest to get when playing Team Deathmatch since the games are short and you can get the accolades with lower numbers than a long game. Also I disable the DLC maps because I like playing the smaller default maps and noobs and less serious players never spend the extra money to get the DLC maps.. I also do all the challenges with a secondary free account so I don’t do any damage to my K/D on my primary account.