Here are some general tactics when playing CS also look at the map tactics section for more in depth on each map.  You do not have to follow these tactics you can learn and develop your own these are what work for me and what I would like other members to try and see if they work for them so we can work better as a team.

1. Weapons- I feel that there is no certain weapon for any map use what feels comfortable to you.

2. Purchase Kevlar and helmet, your primary weapon, ammo, and a HE Grenade- This all depends on how much money you have I think that armor is very important I would sacrifice a better gun to buy ammo if I did not have enough money. If you have a lot of money get a better secondary weapon. I would choose a HE nade over anything else, smoke grenades lag out and people can randomly shoot threw the smoke and mange if not kill you bring your health down a lot. I never use flash bangs either one because I hate when people blind me with them so I don't want to blind other team members and also because they don't inflict any damage a blind person can still shoot randomly and manage to hit you.

3. Watch how the other team plays- On each map learn how they play do they camp, do they rush, do they split their forces up.  You have to learn this so that you know how to base your strategies,  if their whole team rushes one point you do not want to be the only person on your team running to that point I don't care how good you think you are it is pretty hard to take on 8 opponents by yourself in the open

4. Learn how your team plays- You have to see if your team rushed or camps you do not want to rush and have no back up, or have everyone rush and get flanked by the other team.