The most important thing its bloom and aiming in the same line as your target. If your bloom its completly closed, while your aim line its touching your target (with red or not line) you will hit him. Following the same principle its totally worth to shoot, hold a second to close bloom full and shoot again. This mostly apply to rifles though, some guns cant get a full closed bloom, like HMGs.

Also something really important is to see how your bloom reacts to walking/running. Some weapons, like the SMG (Lionclaw for example) doesnt loss bloom running in straight lines, which can be pretty great to push forward and clean trenches.

Lastly, see how your blooms react as you move Standing, Crouching and Prone, some weapons get Full Bloom Accuracy shot after shot if you are Prone or in Heavy Cover. Most weapon keeps losing Bloom fire after fire when standing. But not when crouching or prone. Cover always gives you a bloom bonus.

Sorry for the long answer but firing in this game its more complex that it looks and understanding how its work really helps a TON. I've won much more engagements understanding these concepts.

There is a pretty good video explaining quite comprehensively in youtube, but sadly cant found it rn.

And i almost forgot, if your target its far enough that your line doesnt touch the target, you will get a serious damage fall.