Just follow the steps as shown in the following pictures to make the air core coil for your Fm transmitter.
1. Select magnet wire of specific gauge as described in circuit (buy from motor/fan repairing shop).
2. wound (round up) the wire on a pencil, pen or screw driver of correct diameter as stated in circuit diagram.
3. don't make any half turn without any guide from your circuit text. Remove the pencil, pen or screw driver .
4. Your Coil is almost ready, Cut the extra length of leg's and solder the both leg (pins) of your coil. try to keep the length of leg as minimum as possible. it'll give stability of your frequency.
5. Shrink or expand the coil as the required length as stated in your desired circuit text.
6. Here is your coil