Here I'll show you how to get really neat screenshots, quick and easy!
1. Taking and localizing screenshots
When in-game, playing or as a spectator, press "f5" any time to take a screenshot. Do this as many times as you like as you don't have to paste them somewhere in order to save them.
Close or minimize (Alt+Tab) Counter-Strike and open my computer. Browse to the following directory to find the screenshots you've taken:
[STEAM DIRECTORY]\steamapps[LOGIN NAME/EMAIL]\counter-strike source\cstrike\screenshots
For me it would look like this:
D:\Program Files\Steam\steamapps\oivin1\counter-strike source\cstrike\screenshots
2. Removing the HUD
Open up the console and type in "sv_cheats 1" (You have to be admin or on a local server)
If you want to increase the picture quality (Which you obviously want to) put in "jpeg quality 100" in the console.
To remove the main HUD details type in "cldrawhud 0" To remove the gun model type in "rdrawviewmodel 0" To fly around freely type in "noclip"
UPDATE To remove the cinematic bars in spectator mode type in "hidepanel all" in the console. (Thanks dfggf, nice name btw)
CONSOLE HELP: http://www.fpsbanana.com/tuts/9512