The original "Counter-Strike" doesn't use your Steam user name in the game, and never asks for a name the first time you play. If you don't enter a name in the Options menu, you'll enter your first game as "player," highlighting you as a rookie to every enemy. You can change your name as often as you want -- even in the middle of a game -- so if you get tired of your name or need to add a clan tag, just head back to the Options menu or use the "name" console command.
Use the Options Menu
To change your name before you enter a game, click "Options" on the main menu and enter a new name in the "Player Name" box on the "Multiplayer" tab. Names in "Counter-Strike" can contain spaces, as well as numbers and symbols. You can also reach the menu during a game by pressing "Esc," but because the renaming process takes a few moments, it's best to wait until after you die or between rounds to avoid getting killed and hurting your team.
Use the Console
With a console command, you can change your name slightly faster in the middle of a game without covering much of the action on the screen. Press "~" to open the console. Type "name" without quotes, followed by a space and your new name. For names longer than one word, enclose the entire name inside quotes. Press "Enter" and then "~" to close the console. The change takes effect as soon as you close the console -- press "Tab" to check the scoreboard and see your updated name.