I found at the beginning when I first played that it wasn't as easy as I thought.
Sure I could follow with my eyes, but doing it with a mouse was way harder.
Not to mention that you have to click too which quickly overloads your mind.
I find that eating before you play and getting some sleep helps alot in terms of accuracy.
I don't know why, but it works for me.
The guide for total beginners:
1) Play the easy maps. No you aren't good enough for normal yet.
-If you can't do it, play it on half speed. Get used to pressing x instead of clicking, it helps much more
-Also, try to sync your ears to the beat. No beatmap is there without a beat.
2) Once you're better, go on to normal
-Basically, same thing, just try more. It may take a long time before you can get to hard. I have been playing for a month and I can only manage to get B's and C's on hard.
3) PRACTICE
-I know that some people think that they can get by without actually trying but believe me, you have to practice. Practice makes perfect, right?
Tips:
-To get better at listening to the beat, enable the Hidden mod and try and figure out when you are supposed to click. No peeking!
-To get better at accuracy and to get your body to adjust to new beatmaps, play on Hard Rock. It flips the map over the x axis and makes the hit circles smaller, so accuracy matters more.
P.S. If you find that your cursor is lagging,
1) Go to options
2) Go to frame rate
3) Change FPS to unlimited
This is implemented to keep people from cheating by making the fps low.
Enjoy playing osu!