This is like the best guide if you want to rank up
1. Always warm up before you grind, whether it be The Range or Deathmatch. Maybe even Aim Lab if you wanna practice pure aim.
2. Don't play too much games consecutively, you're bound to get tired for the most part. Take breaks in between if you need to, like every after two games, just stretch your hands and your back.
3. Always play to win, never for stats. You also have to communicate a lot with your team.
4. You could watch a lot of coaching and guides in Youtube, even as specific as the agent you want to learn, then try to apply it to your games.
5. Better if you could record your gameplay, and watch and learn from your successful plays, and learn from the mistakes you made.
rinse and repeat man