Learn the maps Knowing the maps can give you a huge advantage over the other team. Know the angles and the timing to choke points. Also try to find creative ways to flash and smoke certain parts of the map By knowing the maps, you will also know where some good places to hide are and where some the Counter-Terrorist/Terrorist might be hiding as well.
Learn the money system: Knowing or suspecting when the other team has to save or eco could help your team avoid losing a round in which the other team has only pistols
Buy as a team save as a team: You don't want to have 3 guys on your team with pistols and the other 2 with M4s Coordinate so you can all buy at the same time, save at the same time or deagle save at the same time
Crush the other teams economy: Their are a few things you can do that can help you win the money battle Obviously winning rounds is the best way to do this However you can even do some damage to the other teams economy or help your own teams economy with the things you do in a losing round One thing you can do is to save your weapons when you know you can't win the round. A good example of this is when it is a 2V5 situation and their is no way the 2 alive on your team can win the round It is better to have them save their guns then to try to win and end up only killing 2 of the Terrorists. If they live the next round they will have guns, and may also be able to drop a weapon for another one of your team members. Also, to go along with this these two guys can try to get an easy kill before saving their guns. The key is "easy kill" They don't want to put themselves in a situation in which they good easily die. A good example of this is when the Terrorists plant the bomb with 5 members left and only a few members left on your team. Your remaining players can wait for the Terrorists to try to exit the site and then get an easy kill on one or a few of them. On the other side of this, if you are winning a round you want to try to win the round with as little deaths as possible If you have a huge advantage like a 5V2 expect the other team to be saving or trying to get easy kills on your team Try to exit a site with the bomb planted together to avoid deaths