First and foremost you need to identify which team is the "stacked" side on various maps. I'll tell you a few

De_Dust=Ct Side
De_Dust2=Neutral in some cases but most of the time T Side
Inferno= Ct Side
Aztec=Ct Side
Office=T Side
Italy=T Side
Militia=T Side
Prodigy=Ct Side
Assault=T Side

Use "free look" when you are dead to scan the map and see where to go during gameplay. You will notice alot of the time the stacked side will hold alot of campers due to the fact the bombsite or hostage room is farther away from spawn than on some maps. Thats why Dust2 is sometimes neutral. The bomb sites are not that far away from spawn compared to other maps.

You might be asking "why does it matter what team I choose?" Well my friend...when you play on a server for a few maps...you might notice the same players playing on the same side map in and map out. Its not by fluke. Without money you will be toting the glock bb gun and your opponent will have a awp. Thats because the stacked team has full money. The losing team has pistols. Following me here?

The next thing you should always do is crouch when you shoot when possible. I have my crouch button binded to the 'shift' key. This does two things. It improves accuracy. It also makes you a smaller target for the enemy.

Strafing left or right at while shooting at close range is ok as well. You will notice some strafe left and right from long range. Mostly with the ak. Its suppost to be the 'correct' way to use strafing. Small 2-3 bullet bursts. You must become a camper though. In other words you cant do that method wihtout standing in one place moving 2 steps either way. Thats a horrible way to learn the game. I'll explain below.

There are two types of players in FPS games. There are campers, and there are soldiers. Some people take their rank so seriously they resort to hiding in spawn, or hiding in a corner every round of every map. Most of the time with a sniper rifle. Now if your team is getting rolled and you want to camp behind a door 1 or 2 rounds before the team is slaughtered there is nothing wrong with that. You must learn the art of rushing though to be successful in FPS games. You must learn how to run full speed and stop on a dime. You will notice the same type of player that camps alot is also the same type of player that baits alot. I'll touch on that next. By learning how to go full bore you wont ever need to bait a team member to get a kill.

Baiting is very common in FPS games. Basically its when a camper is forced to leave his corner. He uses a team member as his shield and follows him into battle. The camper waits until his team member is engaged then he engages the enemy. Again not every player uses these tactics to succeed. Trust me now that you have been educated in playing styles, you WILL know when you see one of these type of players. My advice? Dont bait your team. Its a real cheezy way to get kills. If you really want to expose someone like this on your team. Look behind you when you start to run around. See who is following you. See if they will run in first or if they are waiting for you to go.

Use the smallest crosshair size you can see on screen. This varies for everyone depending on their video card and monitor. I tend to use yellow and Light blue.

Use headphones and listen for footsteps. Its ok to walk sometimes. I bind my 'walk' key to caps lock. You might have to use voice_enable 0 if people are going crazy on the mic so you can hear the in game sounds.

There are also some console commands that can improve registry. A few I use are below.

CL_Interp 0
Cl_Interp_Ratio 1
Cl_Smooth 0
Cl_Smoothtime 0

You can google exactly what they do if you need to know. They need to be entered every time you start cs.

Ive given you a tutorial on play styles. Not so much technical specifics. Understand you're dealing with a bunch of different players and a bunch of different play styles when you enter a server. Being able to run full speed and seeing the game faster than your opponent is big with online gaming. This applies to many different online games. Once you master that, you can work on changing your in game speed on the fly. Being able to go full bore or slow down to a walk depending on the situation will help you alot.