Accuracy is not only about hitting the circles but also about having proper timing. Listen closely and pay attention to the approach circles to determine the perfect moment to click.
For sliders less than 1 beat long: The beginning of the slider is the most important as it determines your combo. If the slider is small enough you can KIND OF get away with not moving on the slider. THIS IS NOT RECOMMENDED. Follow all sliders with your cursor for practice. If the slider is large though, missing the ball will result in a 100 or even combo break in some cases.
For sliders longer than 1 beat you should hit every part of the slider to get a 300.