Rather than wait for the actual prompt itself, watch the animation of your opponent instead. For instance, take a zombie w/ a golf club or a flaming 2x4 - watch out for the animation when the zombie turns its body all the way back w/ the weapon. The counter prompt won't appear during this animation frame. It's the animation frames from when the zombie starts turning its body TOWARDS you up until the weapon actually hits you.
So you can practice by doing this - wait for the zombie to rear all the way back, wait a second or two, then that's the window frame when the counter prompt should appear. I got the hang of countering (a little too well sometimes) by getting "the feel for when" it appears rather than waiting for it to actually appear. A lot of people try to wait for the counter prompt to pop up only to not press [RT] on time because of delayed reaction. I also suggest watching your opponent's ENTIRE body so you can judge the animation frames yourself and get the hang of it.
The counter prompt for an armed zombie will obviously be different from that of an armed or a mutated J'avo. Since a J'avo can stab you quicker w/ its knife than a zombie can pummel you w/ a golf club, the animation frame window for the counter prompt will definitely be shorter.
For certain stages:
It helps to play with a seasoned veteran (or one that is at least very patient and understanding that you're really trying) who knows the stage very well. While you're running around grabbing Time Bonuses, make sure you're also grabbing healing items (herbs, First Aid Sprays), grenades, and land mines since these are located near or around the Time Bonuses. Also, it really helps to know the enemy spawn points and where to go at during certain kill counts.
For example in Urban Chaos, around kill #10, the policemen spawn in the area by the butcher shop and the faraway Combo Bonus. When dogs start appearing around kill #15 - 20 in that same area (they seem to spawn from within the butcher shop), I try to run in circles around them rather than running towards them in a straight line. That way, they will have a harder time pouncing on me and will have to turn around just to face me. Around kill #46 - 48, you or your partner should run up the stairs to the sky bridge to kill the swat zombie w/ the machine gun. Also, there's an explosive oil drum you can shoot to kill the other two swat zombies. Around kill #70 - 80, the bloodshots start coming in. If you're not good at countering, stun them with a flash grenade, an acid round, or a sniper rifle/magnum round. Heck, you can even round them up and blow them up a grenade or slide through them and plant a land mine (<-- this tactic works well against Whoppers).
Well, best of luck to you. If you ever need help, feel free to message or add me on XBL.
^^ chocoblue - do u know the spawn points for Requiem? I'd really like to learn them. Thanks.
On solo it shouldn't be that hard to find the enemies, but one spot point I know is behind the fence next to the green herb. You should fight in that area most of the time.
On Duo, my partner or I tend to be in the sewers for at least 25 to 30 something kills because they seem to spawn and like going down there. While the other person is just getting Timers everywhere. Then after, me and my partner tend to fight the enemies on top and they don't seem to be ever in the sewers.