On the command line of a shortcut to Half-Life (HL.exe) you add
-console to the end of the pathname. (Do this by right clicking on the icon, and selecting Properties. This should bring up a window with 3 tabs. Select the tab called Shortcut, and you will see a textbox with the pathname of your HL.exe, add -console to the end of it.) Then in a game, u press the ~ key (its called a Tilde guys, pronounced TILL-dee
) this will open the console!