Let's get to it.
1. Obviously, don't place your crosshair over people through walls while using ESP. This is pretty obvious.
2. Die sometimes. If you're walking past someone in a corner, and you know someone is there, don't always kill them there. Walk past to make them kill you, this looks very legit.
3. Peeking. If you know there's someone around in area you're going too, don't have your crosshair where they are going to be peeking! Place it somewhere else, so when they peek, you can simple adjust your crosshair to them and kill them.
4. Check places constantly. It's a bit suspicious if you go a whole game without checking a certain spot, and then when someone is there, you only check it then. Always try and check the same spots and have a general pattern.
5. Use VisualESP. If your cheat has a visual esp feature, (it shows up a different colour if you can see them) use it! It's very useful to make sure you're not shooting when you can't see them.
6. Check your score. If you're going something ridiculous like 30 - 0 - 5, it might be a good idea to die purposely every once in a while to avoid reports. (Or just say that you're smurfing)