terraintactics

There are certain tactics that are unique to each landscape.
Water
Water combat sucks. If you want to kill youself instantly, unload any explosive device underwater. Notice you cannot strafe underwater or swim backwards, so your movement is very limited. If you have the SLIGHTEST inkling that you are being followed under water, the stupidest, most novice thing to do is to turn around. In the time it takes you to do that, you'll have a knife up your butt so deep you'll need a... Anyway, I hope I made my point. Once you grab an enemy flag and begin swimming, don't turn around for anything. What you do need to do is to turn around immediately after you surface from the water and run backwards if needed. If you have a SAW or any grenades left, the best bet is to unload on the point you just surfaced from, because enemies will typically trail you by following your exact path.

On the subject, when you emerge from the water and know there's danger on the land ahead, don't be stupid and just jump out. Strafe immediately as you emerge, as if you had been deathmatching on flat ground the entire time.

As limiting as the water is, there are many hit and run tactics that can be used on the water-land BOUNDARY. Jumping in and resurfacing somewhere else is a superior confusion technique. Experiment with this concept extensively... There are many strategies to be used on the water-land boundary.

Jumping out of the water and strafing really quickly and then jumping back in is an effective technique to confuse pursuers on the ICE FLOWS board.

Also keep in mind that as a DF soldier, you can stay submerged indefinitely. Something like that, anyway. Use it to your advantage. On more than one occasion, I've sat under water for a minute or two to wait for a friend so we could launch an attack.

Knifings under water suck, as I said. It's like jousting. You basically have to hope you have the right timing and pull/swing your knife at the right instant as you're swimming towards an assailant and he's doing the same. Both me and my assailant have knifed each other at the same time sometimes... Anyhow, I usually wouldn't trust the odds associated with knife jousting under water to do it too often. You might as well jump out of the water and drop some grenades on the other guy instead. You have much better odds that way.

I apologize if I conveyed the idea that knives are the only mode of combat underwater. Claymores can also be planted to catch very unsuspecting victims. The only problem is that most sections of the water are either trafficked very often or nearly never, so its hit and miss whether you're going to end up blowing the enemy, a teammate, or even yourself up.

Claymores can also be used as an active offensive weapon. Since they explode forward, you can prevent a knifing fiasco by laying a claymore down in front of a charging enemy. "You can lay one in front of someone coming to you (damn novices), or just set them around, hoping someone swims by, but stay clear of your own." -- SAS GUNNY SGT. Thanks goes to Gunny for providing me with the info on claymores in the water.

One more thing. When you swim into enemy territory, stay LOW! Not only are you harder to detect and are less of a target, I haven't confirmed it but I think the lower you are, the less likely that a grenade being dropped into the water will kill you. Grenades are like depth charges, so stay low.

Plains
An open, level plain is the easiest place for a SAW player to rack up kills. Conversely, snipers, don't try doing anything but running when you're in the open. Open flat land in general is not the smartest place to do anything because there's no cover. Stay out of the open. SAW players even should opt to seek cover rather than fight in the open; you have a much better chance by going in close and deathmatching than attracting the attention of enemy snipers.

Running in the open
This should be obvious. Don't run in a straight line when you're running in the open, and never run towards an enemy directly. There's nothing as easy to shoot as a soldier that doesn't move sideways. When you need to cover some distance and you just don't have time to deal with the sniper that's taking pot shots at you:

1) Run then hit the prone button. Then release it and run again. Stopping and starting erratically always screws up snipers' lead time.
2) Run in circles. Zig zag towards the direction you want to head in. Run up steep slopes so you fall down them. To a sniper with any lag (even me on my T1... don't ask me why, I don't know), it sometimes looks like you're teleporting around the place. There's nothing that pisses me off more when I'm a sniper than a teleporting flag runner.

Of course, if you're trying to evade a SAW player as opposed to a sniper, you won't make it. Even the worst SAW players can shoot you dead in a matter of seconds in an open field. You need to seek ditches and valleys, there's just no evading a SAW player in an open field... And when you do get to cover, turn and confront the SAW player as soon as he comes over the ridge. The element of surprise is your best weapon in such a scenario.