This from C3PO

Air to air refuelling has been subjected to a major overhaul. This has resulted in a complete rewrite of the tanker and receiving aircraft AI.
The flight leader may request refuelling and this is on behalf of the entire flight. If another flight member requests fuel, the request is for the single aircraft.

The way the player aircraft behaves depends upon the player options. In easy mode, the player simply needs to line up approximately behind the tanker, and the new AI will take control and refuel the aircraft. In simplified mode, the AI has one hand on the aircraft along with the player. The AI and player controls are mixed together. As the aircraft moves nearer the tanker, the player has less influence over the movement. The AI provides most the throttle control, with the player throttle control becoming a modifier, allowing some influence over the speed of the jet.

In both Easy and Simplified mode, the AI will open and close the refuelling door, plus make a “ready for gas” radio call when stabilised behind the tanker. Once the jet is refuelled, the AI will make the “Done refuelling” radio call.

In Realistic mode, the player has full control over the jet in all respects. He must open and close the refuelling door manually, fly the jet into position, make a “ready for gas” radio call, fly the aircraft to the boom and once refuelled, make a “Done refuelling” radio call. Then fly into the waiting position until all jets in the flight have been serviced.

In all modes, once the refuelling door is opened, the flight control computer dampens the control surfaces. This permits the pilot to make small control movements with ease.

Major changes have occurred to the AI for the tanker and thirsty aircraft to eliminate completely the rapid jitter that occurs in FalconAF when refuelling takes place. The AI is now able to refuel during a tanker turn, and the tanker turns are now distributed in multiplayer so that the turn is consistent between clients.
The tanker no longer struggles to maintain a constant speed or altitude during refuelling.

After refuelling, the thirsty aircraft reduces speed and decreases altitude slightly before sliding across to the waiting position. Meanwhile, the tanker will increase its speed by a few kts only during decoupling before settling back to the previous refuelling speed. The tanker altitude will not vary between refuelling aircraft from the same flight. Tanker boom should now visibly connect in MP.

We will be trying the refuelling level on realistic when 1.06 come out so practice it offline and make sure you know the procedure. If a refuel is authorised by the flight lead, pilots who do not know the correct procedure will wait until last to refuel.