If you care enough about CS:S to the point that you want to make it a small goal to be really good you're going to have to do a few things.
When I started playing in Spring of '06 I had a standard HP pc.
this thing could get me at MOST 40 Fps on rare occasions at 600x800.
While I learned to scout and play CS in general like this, I knew I was missing out.
Bottom line is that you're going to have to either throw down money for a better PC and GPU and sound card as well, or make your own gaming rig that will be for games only/mainly.
I'm pretty sure most of the players that get these ridiculous scores and go through the game with an almost 6th sense of pwning have rigs meant to handle CS:S and PC games or at least have money invested in hardware that really gives you an edge.
The five things I can tell you that made
me go from being "average" to "good" are as follows.
1. Mouse [logitech mx518] get something made for gaming. 1600 dpi is always nice.
2. Sound Card [SB Audigy SE] cheap, and works wonders on the ears.
3. Video Card [nVidia GTS 8800] not so cheap, but you can be sure your system is up to par with today's games.
4. Decent internet [comcastfail] this varies so yeah.
5. Practice. [hours, hours, hours.] obvious tip is obvious.
This is from MY personal experience and while many many many of you have your own ways of doing things, all I can recommend is you get some power in your system so you know it can keep up with you, as well as the game.

And learn the maps as best as you can.
Pay attention to alll the details that matter and don't matter.
There are so many ways a single round can go and the dynamics of your gameplay have to change constantly on whatever map you're playing.
Unless you play office or something and T's just feel like camping projector.
But hey, if you're playing and getting frustrated, these things can help you greatly almost instantly, but in the end....
YOU have to take the time to find out what YOU're doing wrong or right , and apply it to the way you play.
Watch other players, see what they do.
Why they go here, or there.
Notice the way some players zone in on one thing and how others are constantly scanning every direction around them.
All I can say is the best way to not get flanked is to take it upon yourself [especially with group rushes] to stay back and make it your responsibility to watch the rear and call out any hostiles.
I do this lots on highschool and have taken out countless people an d possibly saved my team from being ownd.
But if these are things that YOU know that YOU are having problems with, see if changing/adding hardware to your pc will help.
And just keep playing.
I swear, eventually you will begin to understand cs and all of it and just let go and get lost in the game.
When you can go from normal everyday mode and then sit down and get in that zone, things will brighten up for you my friend.
MOST IMPORTANTLY: YOU ARE NOT A NOOB OR NEWB OR NooB!
Never let other player's terms get to you, or any gaming/internet lingo.
I hate that so much when people apologize for being newb or a noob.
ITS NOT YOUR FAULT YOU DON'T KNOW HOW TO PLANT A BOMB OR DO SOMETHING SUPER OBVIOUS!
WE WERE ALL THERE AT ONE POINT!
Anyone who constantly calls others noobs because they don't know how to do something irks me so much.
Tell them how to do it!
And ask for help!
Pepsi, you are a good player, everyone in eGO is a good player.
I just get so frustrated when people think it's bad to be new or some crime to not be AMAZINGGGG.
Just play man.
And if you everrrrr need help or tips, ask me.
I love giving others insight into things I know.
Because I know how it feels to be out of the loop, or like old man said it seems like everyone's cheating sometimes because you just are doing soo bad certain days.
Just let go, play, have fun, and understand it's just a game and that the whole concept of games and computer entertainment is for YOU to have FUN.
/post.