dont cheat.
HL: obviously raise in game volume but also I think that the most important thing about learning how to not die to spies is avoiding decloak timings, spies dont decloak randomly because its easy to be constantly checking behind you then, its about getting good at dealing with spies decloaking as combo spams, or as ubers fade, or as you're walking through a choke.... I watched a lot of spy demos to try to improve at this
6s: similar but also think about when they might spawn spy, 6s is more random about this because youre not going to be as vigilant all of the time as in HL, but try to watch for the obvious timings at least, stuff like pushing out of last with uber ad after killing most of their players on last