Killzone 2 tactics
The best strategy is for a tactician to place a spawn point right behind the enemy normal spawn usually underground so its not camped. However, if they start camping the spawn call it out so people stop walking into their demise. Pop up another spawn point grenade somewhere else as a back up.
As for the other classes Assault is always good to play as or generally anything you want. A Saboteur is always fun to have in this mode to especially when a Tact places a spawn near theirs and you come up behind them. If you are going to play as a medic try not to resurrect anyone in the line of fire because that is usually another kill for the enemy. At the most try to have someone give some cover fire while you do it to get our buddy out of the way. A great cover fire class is a soldier with the huge LMG forgot name but its big and it has lots of ammo like the RPD in COD4. The engineers need to be sneaky place your turrets in places they will not see well or hidden a great place for them is on roofs because very few people look up while they are sprinting around. Which is another great reason why taking the high road is fantastic.
Keep your eyes out for enemy Saboteur you will have a red reticule when you place it over them. They will have an allies name and wardrobe so they are hard to spot in a fire fight. My trick to catching them is they don't show up on radar so if they is a guy running around in front of you and he is not on radar blast em.
Search and Destroy
This is the mode where the engineer
really shows what he's made of. If you can load down that defense area with turrets out the wazoo it is much much easier to defend it. I believe the limit is 5 per map per side so that is 2 per engineer so we should have about 3. Also they can repair those .50 cal guns and these can make a huge difference. If you repair it and get an assault class in it they get an added bonus of armor from the gun on top of their already added bonus which makes them a tank with a big gun.
The Saboteur is also great to get into the enemies defense area and blast them with his C4. You can wipe out the entire team with one good one and then its easy to get in and plant the bombs. Medics are very important in this game mode because they resurrect our fallen buddies and this can be the difference between a win or a loss. As for the other jobs just play them how you normally play an assault is good at keeping people out of the area with a rocket. Snipers are good at getting people from the sides that try to run across.
VIP protect or kill
These modes are usually dominated by people playing Assault. Because well you can sprint in and blast the guy with your rocket and your also a great meat shield to protect the VIP. I have never tried this but I wonder if the VIP can be a sniper and go invisible lol. I never seen it done during the beta but its worth a shot. I bet the computer does not pick people playing as snipers.
Also super important if you get killed DO NOT RESPAWN you can sit there dead calling for help and as long as they do not finish you off you will win also a medic can bring you back. I cannot believe how many times we have won because they could not get in to finish the guy off after they killed him initially.
This is another mode where the Engineer shines. They can repair those .50 cal guns and make it real easy to keep a spot. Their turrets also help a whole lot. Another great place for some Sabo C4 to clear the area of enemies. This is where we have to camp the area I know you guys are not big on camping but its the easiest way to win this. The other classes are free to play how they normally do kill the enemy keep the spots safe. Snipers get a lot of kills here because most people are to worried to get to the spot then to look for an invisible guy on the roof and its real easy to blast someone in the head when they are standing still at a point. With that being said keep moving around the area you do not have to stand completely still to capture it you can move around in the area and still get it.
Capture the Flag (Propaganda Speakers)
This is also a lot of fun because everybody is going for the one speaker and you have to place it in the heart of the enemy base. This usually turns into a frag fest real fast. In this mode it is probably the best mode for Tacticians to place spawn points right on the drop off area and to call in air support. Because people are going to be running for their lives to the spot and your little air bot can blast em. Turrets and any other type of defense measures are also great. Assault also shines in this mode as the carrier because of their extra body armor and sprint ability. All you have to do is run into the place no setting there putting it in just touch it so run in there and kamikaze that TD. Yes you will probably die but your going to make the team win hehe.