Assault Trooper 15
Complete a mission by firing only assault rifles. Melee attacks don't count.
On the second mission of the game you can use the BAR for this achievement. Be precious with your ammunition as it is not plentiful. You can also use an enemies MP44. If you have problems with this, try it on Easy difficulty. Some have been saying that you cannot use grenades or melee attacks if you want to get this one.
Battlefield Scavenger 15
Complete a mission by firing only German weapons. Melee attacks don't count.
You can obtain this achievement as well as "Rifleman" on the first British mission. Knock out the first guard and use his rifle for the rest of the level.
Still Ticking 30
Complete a mission without dying or using checkpoints.
Simply complete a level without dying. This is done easiest on the first level at Saint Lo, just keep your head down and shoot occasionally to help your teammates (who will help out a lot) keep the enemy at bay. You can do this on any difficulty, but obviously its easier on Easy. You can also get the "Allergic to Bullets" and "Conservationist" achievements on this level.
Allergic to Bullets 25
Avoid getting hit more than 30 times during a mission.
Simply complete a level and don't get hit more than 30 times. Make sure to count how many times you are hit and if you think you've failed before the end, restart te level. This is done easiest on the first level at Saint Lo, just keep your head down and shoot occasionally to help your teammates (who will help out a lot) keep the enemy at bay. You can do this on any difficulty, but obviously its easier on Easy. You can also get the "Still Ticking" and "Conservationist" achievements on this level.
Complete a mission using less than 300 rounds of ammunition.
Simply complete a level without firing more than 300 rounds. This is done easiest on the first level at Saint Lo, where you can rely on your comrades a lot, and then use a rifle as opposed to an automatic weapon as it will use up less ammunition. You can do this on any difficulty, but obviously its easier on Easy. You can also get the "Still Ticking" and "Allergic to Bullets" achievements on this level.
Close Quarter Combatant 100
Complete a mission without firing a round. Player can make use of melee attacks and hand grenades.
Try getting this on the second level, 'The Island'. Use the butt of a rifle as it takes out the enemy with one hit, and make use of hand grenades when there is more than one enemy to take down.You can do this on any difficulty, but obviously its easier on Easy.
Grizzled Veteran 150
Complete the Single Player Campaign on Veteran difficulty.
Some Tips that may help :
* Good use of smoke grenades is a vital part of the game, use them well and in the right places and it will make this a hell of a lot easier. Remember not to waste them though, as smoke grenades are not in plentiful supply.
* Move slowly but steadily. Always aim Center Mass, forget about Headshots. Don't underestimate your enemies or you'll die. When there are fixed machine guns, use grenades and smoke grenades. They will save you.
* Always stay behind cover - try not to get stranded in the open or the enemy will often take you down. When reloading always do it behind cover as getting caught mid-reload will often end up with you dying.
* Always make good use of your fellow comrades. They will often be a great help and take out a number of enemies for you. They will not do all the fighting for you and you will be kept very busy, but staying behind while your fellow country men storm a house will often save you dying instead.
* When you get shot, as soon as the screen flashes and judders, get to cover as quickly as possible. This flashing screen means if you're shot again you will die. Stay in cover until the screen returns to normal.
* Always keep a careful eye on the grenade indicator, as soon as it pops up, be somewhere else. Alternatively, you can try throwing the grenade back at the enemy.
* Choose your weapons carefully, when fighting in close proximity to the enemy an automatic weapon is always the best choice. A rifle is the best choice for the enemies at long range. Be sure to carry one machine gun and one mid to long range rifle at all times.
* When clearing houses of the enemy, grenades are the weapon of choice. Remember they will bounce off walls if you want to clear the enemies around corners without the risk of being shot.
* If your stuck on a certain mission for a long time, try a different strategy, head a different way, or try something different to what you have been doing previously. Different strategies will work for different people and there a various ways around many of the obstacles.
(Thanks to snafegeeza & Carl Showalter who composed this Veteran tips list for Call of Duty 2