tier d pavlov autism brick or How You Learned to Abandon the Suck and Embrace Teamplay aka please work together 
most of this is assuming that someone taking advice from this is a ""lower tier"" newer player, or someone who habitually discredits themselves/dislikes their gameplay, ect- anyone unfamiliar with the content past the surface of CS, rather than the absolute most surface core gameplay loop. Mostly focusing on teamplay, objective play and plays, what you should be worrying about instead of whether or not your vrbf is gonna like your new shoes, ect.

Starting off, your absolute core focuses, the thing that you should absolutely be focusing on 95% of the time, and the things you do to make it happen- getting the little victory popup at the end so you can talk big shit in Discord afterwards- planting the fucking bomb if you're attacking, and stopping those overdressed airsoft players from planting their bomb if you're defending. This is largely reliant on team coordination to host a good offense and defense, which I'm gonna do in it's own section, but ultimately your focus every round should be "where is the bomb" or "how do I defend/remove this bomb without getting my cheeks clapped rosy red." Just fussing about this alone instead of your own survival is a monumental step forward for a lot of the regulars who squalor a bit.
The reason I don't say "fuss about depopulating the enemy team" as so many of those fabled Tier-S+ epic gamer gods do, is because you're focusing on the complete wrong objective in doing so. Yeah, elimination victories are still victories, but going for kills over the objective means that you can't leverage your defensive advantages wherever you may earn them (onsite as defender, post-plant as attacker), but primarily because you're not good enough to do it. Stop fussing about your own KDR, match up with a few other shitters, and get a 3-man squad going to get the bomb down rather then wandering alone. 
cont