Radd's School of rotary flight has a very detailed description of how to fly helicopter. Many people learned to fly that way. Basically, is a general concept of crawl, walk, run approach to flying helicopter baby step at a time. Not going to repeat all that. Definitely worth reading a few pages to get the idea. Don't have to follow every step like they say.
This page adds to what is not mentioned there. This page gets to the technical reason of why helicopter flying can be so difficult, and how to get to the point where you "get it".
Why helicopter is different.
This is why, and is difficult to understand. When you finally learn to fly, you will intuitively understand it.:The sticks on the helicopter radio controls the change of accleration.
Understanding Movement of the Helicopter:
The most difficult part of flying the helicopter is the right stick on the radio. It controlls the pitch and roll. You need this stick to move the helicopter from one location to another.
The right stick controlls the rate of roll, and not position or speed. Beginners will think by pushing the stick left slightly, helicopter will fly left slowly. Wrong! Pushing the stick left will cause the helicopter to roll to the left. This means if you push the stick left slightly and wait, the helicopter will continue to roll until is upside down or more likely crash. But way before crashing, it will start moving left slowly at first. The beginner will think the helicopter is in control, but then it will continue to gather speed faster and faster until going quite fast. By then, helicopter is quite hard to control.
Right stick moving left and right is the roll. Start with roll first. Roll means the helicopter rolls over until is upside down. Stick position controlls how fast the roll rate is. Small stick means helicopter rolls over slowly. Big stick input means helicopter rolls over quickly. Don't give big stick unless you want to flip the helicopter over unsidedown quickly. Very important to realize stick position controlls roll rate and not roll position.
The final angle of the roll determines the acceleration of the helicopter. This means if the helicopter is tilted 1 degree, it will accelerate sideway slowly. If is tilted 2 degrees, it will accelerate twice as fast. Notice I say acceleration and not speed. Mean if you leave the helicopter tilted 1 degree, it will continue to accelerate sideway until is at supersonic speed. Ok, not that fast, but it will eventually go pretty fast. The bigger the tilt, the faster it will accelerate. So just because you don't see the helicopter going sideway that fast, and is highly tilted, don't wait, because it will continue to buildup speed going sideway until is going sideway very fast.
Lets stop and think about the concept a little.
Position is where the helicopter is at. That is what you want to control.
Speed is how fast the helicopter is going. Speed is how you get from point A to point B. Can't change position without having some speed.
Accleration is how much speed is changing. As in going from 0mph to 5mph in a one seconds. The amount the helicopter is tilted affects its acceleration.
Change of Acceleration is how much acceleration is being changed. That means going from slow acceleration to fast acceleration. That is what the stick on the radio actually controls. The more you push on the stick the faster the change in acceleration. Change of acceleration in calculus is the 3rd derivative of position. Not so intuitive, and is why flying a helicopter is not that intuitive. And is why helicopter get out of control.
Putting it all together. Let say you want to fly the helicopter from point A to point B 10 feet away.
That is a lot to go from one location to another. Keep this in the back of your mind. At some point, this becomes intuitive, and you will "get it". Is good to understand the concept behind it. Is a lot of basic physics.
Throttle is much easier to learn than the right stick. Is much more intuitive. Assume middle throttle is where lift balance gravity on a helicopter. This means at middle throttle helicopter keeps its vertical speed. Putting the throttle stick in the middle does NOT mean the helicopter stops in mid air. Very important when decending. If you are going down at a pretty good clip, realize just because you move the stick to middle does not mean helicopter will stop decending. It just mean it will keep decending at the same rate until it crash into the ground. Remember, it takes extra force to decellerate. So is important to move the stick up to decelerate as you approach the ground. Ideally, vertical speed should be zero when you touch down. Push the stick up too long or too hard, and the helicopter will stop decelerating and start to fly upward again.
After you know how to position the helicopter, and understanding stick controlls the third derivative and all that. At least the subconscious mind will understands the third derivitive and how the helicopter moves. Next hard task is orientation. The most difficult part is when the helicopter is facing you. One way to solve that is to write "L" and "R" to the canopy. That way, you know which way is right and left. Ultimately, key is memorizing what is left and what is right. Forward and back is usually easier. For left and right, have to practice it enough to make it intuitive.
Regardless of what you do to remember right and left, ultimately, you want to put orientation into the non-declarative memory. That is long term memory. Is like going home from work. You know how to do it without thinking. The memory is already in the back of the mind, and you don't have to think to know what to do.
Upside down orientation is more difficult. Here are some mnemonics to help out.
Roll: Roll is easy in upside down. Roll direction stays the same whether is right side up or upsidedown. So just imagine the helicopter is still right side up for the roll. If helicopter is facing away from you, left is left and right is right. If is facing you, the left and right is opposite, but that is the way a normal helicopter is anyway. So if you are comfortable with head in normal flight, then upside down for roll is the same.
Pitch: Pitch is opposite. One way to remember pitch is to imagine you are flying an airplane in a video game. (At least the old video games when I was a kid. Don't know about games now) Down stick is pitch down, and up stick is pitch up. To go forward, you have to pitch the nose down. Therefore, use down stick. Pitch nose up to go backward, so use up stick.Yaw: For left and right yaw, is also opposite. One way to remember is you are holding the tail with your hand. Left stick is moving the tail to the left, and right stick is moving the tail to the right.
Throttle: Of course, when upside down, down is negative pitch, so use down to go up. I never really had too much trouble with this one.
In flight simulation, do many flip over and back to normal. Learn to adopt to different orientation quickly. Then you are ready to fly the helicopter upside down.