
Here are some map tactics that you can try out I get real in depth with dust because on their server we play at that is in rotation more than anything, other maps I will touch upon. These are general map tactics they will not work every time
Dust

Counter Terrorist:
First off you need to learn how your team work to decide where you are going. If you choose to spawn camp I will not touch upon that I never spawn camp. If the T's are rushing the hall and your team is getting raped or they are not very good then I would suggest going the bridge the best way to do this is to go to the left of the hallway and take a look over the bridge before blindly running in, if it looks good jump on down and rush to the left side for cover in case of snipers or T's you couldn't see from your point, if it looks clear move up the path looking behind boxes and come up on the other side always checking you back and sides for a camper, when you safely reach the other side you need to decide where to go from there, keep track of who on your team is dying if a lot of them are dead then T's are camping hallway or rushed threw in that case go left and head to the hallway to flank the T's if it seems they didn't rush go right and see if they are spawn camping or if they are hanging around in boxes. ALWAYS check the boxes on the right in the T's camp this is a notorious place for campers to be jump by hit shooting a burst of fire if no one is there then just reload and move on if there is someone and your burst didn't kill them finish them off and move on. If you decide to hit the hallway there are a couple ways to do it, if T's rush the hall I would suggest going to the left hall entrance that was you can come up on their side, I usually get on the bridge and come around the corner on top in case any T's made it threw I can get the drop on them, then continue down the hallway either heading towards the bomb site or take a left into T territory, if the T's have been camping that hall I would suggest emptying a half a clip into that crate in case someone is sitting there or run a round facing that way. After making it by if you do not hear anything look to the right first if it looks clear rush out looking to the left and then the right again, if you have rushed threw quickly enough head to the bridge and come up behind the T's if not look around and get any T's left around.
Terrorist
Again decide how the other team works if you decide to rush the hallway look bring an HE nade and throw it towards the left and look to the right make sure no one is flanking you, then make you decision from there on which way you want to go, look out for rushing CT's and any campers set up. If you are getting rushed every time I suggest either setting up outside the hallway with your team and catching them in a cross fire when they come out, you have to watch your ass here make sure they don't come up from the bridge and get you. Another thing you can do if you are getting rushed is take someone with you and go bride and come up behind the CT's. A big mistake people make is sending their whole team one way you can not all rush the bridge if all the CT's are not you leave the hall wide open and they will get threw you have to split up evenly to defend or attack both sides.
Militia

I won't get as in depth on the rest of the map but some general tactics for militia is again learn the other team, use the tunnels to your advantage if you are a lone terrorist you can hold on the ct team for awhile and be able to retreat up a ladder or rush the tunnels and come up behind them, it also works good to grab a sniper rifle and get on top of the house and take out people from there. On the CT side it is also good to use a sniper rifle to anti snipe the T's you can also rush the tunnels very quickly and overtake the T's.
Assault

On assault if you are a T you can choose to rush the CT's which usually works really good they do not expect this, or you can camp the warehouse and wait for them As a CT rushing the back door is usually good there isn't as much of a wide area that the T's can hit you coming threw the front there is a long way to run for cover if they are set up good.
Inferno

This is a great map as a CT you can rush the right full force and clean up pretty good or head to the left and snipe from the room, if you notice you can shoot threw the holes in the window coverings but a camping T can also see you move behind it a good way to do this is crouch when you enter the room and move the the left side and pop up behind that window usually they are looking at the right one and not expecting you to come up anywhere else. If T's decide to camp the building it gets a little trickier, get some nade and smoke and flashes and throw them threw door and rush up the stairs or camp outside and wait for them to run across the catwalk and get them there. If you are a T you can rush up any side watching for snipers in the open spots especially if AWP is allowed CT's can snipe you while you run threw all the open spaces. Camping the building works real good CT's only have one way to come in and you can hold them off long enough to flank them.