1. Load up Half Life (or HL MOD).

2. Load up the map you wish to start recording a demo on.

3. When ready to record the demo, bring down the console (`) and type
    record <demoname> (where <demoname> is the name you wish to call your demo).
    e.g. record "m00".
The demo will now begin recording and will continue to do so until you tell it to stop.

4. To stop the demo type
    stop in the console.
(note, if you do not end a demo before changing map or quitting the game, there is a chance that the demo will corrupt).

5. To view the demo, bring down the console and type
    Playdemo <demoname> <playback speed> (where <playback speed> is an integer, 1 being normal playback speed).

And that's about covered everything you already knew, so how about some rather nifty little commands for making the demo look a little more professional?

6. To continue recording onto the same demo type,
    Appenddemo <demoname> in the console
(This is a good idea if you want to continue recording of a clan match into the same file).

7. After completion of the full demo you can now type
    listdemo <demoname> in the console to get a full list of all the indexed sections of the demo
(i.e. 1 section for each time you appended the demo and thus recorded a new section).

8. You can remove individual sections of the demo by typing
   removedemo <demoname> <sectionnumber>
N.B. DON'T remove section 1 (i.e. "removedemo m00 1" as this will corrupt the demo).
Once a section is removed, the following section takes its place (e.g. you have 5 sections in a demo and you remove section 4, the old section 5 will now become section 4).

9. If you wish to swap sections of the demo around you can do this by using the
swapdemo <demoname> <section a> <section b> command
(where <section a> and <section b> are the sections you wish to swap).
N.B. DON'T swap section 1 with any section as this will corrupt the demo).

10. Finally, you can modify each section to contain a title, play at a certain speed and set the section to fade in or fade out. Do this by using the following command
    setdemoinfo <demoname> <sectionnumber> <title "titlehere"> <fade in|out fast|slow>
(where "titlehere" is the text you wish to appear on screen briefly as the section plays, and were <fade in|out fast|slow> sets the section to fade in or out either fast or slow).
e.g. setdemoinfo m00 1 title "Oh My GOD! You look like a cow" fade out slow

11. Your demo is modified and saved as you work, so it may be a good idea to create a backup of the recorded demo before editing. Demos are saved to the base directory of Half-Life (or in the base directory of the HL mod you are playing, e.g. "\sierra\half-life\cstrike\").