Both games implement some combination of or have variations for each of the following features:
- Scope sway
- Gravity induced bullet drop
- Bullet travel time
- Body posture
- Clothing (Ghillies)
- Tools
Battlefield:BC2
Scope sway
None. BC2 does not implement a "breathing" aspect for sniping. Thus your crosshairs are stationary unless you move them.
Gravity induced bullet drop
Yes. As range to target increases the actual point-of-impact of your round with relation to the center-point of your crosshair increases.
With very long range laterally moving targets you have to put their torso in the lower-left/right quadrant of the scope and fire to get a hit.
I feel that it makes stationary target sniping ridiculously easy compared to MW2, but makes it harder to hit moving targets.
Bullet travel time
Yes. You must lead targets that are in motion.
Body posture
You cannot go fully prone in BC2. You can only kneel.
Clothing
Snipers wear ghillie suits. Their utility can be limited since they cannot go fully prone. It is still useful in large bushes and trees though.
Tools
There are no thermal scopes, heartbeat sensors, AC-130's or other anti-sniper elements in this game.
Call of Duty:MW2
Scope Sway
Yes. MW2 implements a "breathing" aspect for sniping. Thus, when completely stationary your crosshair will bob semi-randomly.
You can also "hold your breath" for a short amount of time which reduces the movement, though not completely.
Gravity induced bullet drop
None. Whatever is under the center-point of your crosshair when you pull the trigger is what gets hit.
Bullet travel time
Yes. You must lead targets that are in motion.
Body posture
You can go fully prone in MW2. This decreases scope sway and makes you harder to see.
Clothing
Snipers can wear ghillie suits. The suit must be unlocked. Different camouflage colorings can also be unlocked.
Tools
As a sniper you can unlock a thermal scope which makes sniping super easy-mode.
However, you are also terribly vulnerable to things like AC-130's, Harriers, etc. unless you are using cold-blooded.
Best Answer
First of all, you should have a fairly good idea of the map layout. That way, you'll know what to expect, and from where. Learn common hiding places.
The Strategy
Stay out of his line of sight. Use available cover at all times. Don't just run around in the open. If you know there's a sniper nearby, take an alternate route and surprise him, or just avoid him entirely. Avoid choke points, as snipers usually cover those.
The Tactics
When a sniper is actively targeting you, move. Take your shots at him if you have to, but do not stand still. You're asking to get shot in the head if you do. Move unpredictably and chaotically. Jump, run back and forth, anything that you think he isn't expecting. He won't miss if he can predict where you'll be, so you've got to make sure he can't do that.
In that situation I personally would figure a way to flee and flank him. If you don't have a sniper rifle, you're at a disadvantage at a distance.