How to Mount a Servo Motor
Servo motors require a solid mounted position to perform as they are designed. In order to maximize efficiency and torque from the motor, ridgidly fix servos to a solid frame or other portion of the object you are trying to make move. The best way to mount the servo is based on cost and how frequently the servo will need to be replaced.
Many applications like robotics and large model airplanes allow proper attachment with a universal servo mounting bracket or a 
specialized vertical or metal mount. Universal servo mounts are not overly expensive, but they require space for installation. Many compact radio control vehicles, robots and animatronics do not provide enough space for using pre-made servo mount brackets. When not using a specialized servo bracket, the position of the built-in mounting bracket on standard servo motors makes it very difficult for attachement with a bolt and nut combination. The mounting holes are so close to the servo body that holding a nut while tightening a bolt through the openings is extremely difficult.
Using a treaded bolt is possible, but there are two issues. If a universal or other special bracket is used, the same space constraints existing with attaching the bracket to the frame. A tap and die set might make it possible to directly connect a threaded bolt through the servo mounting holes into a frame or other rigid piece.
Mounting a Servo Using Cable Ties
The quickest way to attach a servo motor to a frame is by using nylon cable ties, sometimes called zip cords. 
Cable ties are cheap, lightweight, and available at almost any hardware store. Some additional work may be needed to properly attach linkages or cables when cable ties are used to get everything in the right position. Cable ties are also easily cut to remove and replace a servo motor when needed. A new cable tie is again used to reattach the new servo motor.
Mounting a Servo Using a Hot Glue Gun
Another quick and inexpensive solution for mounting servo motors is to use a hot glue gun. This method is frequently used by model airplane hobbyists. Glue is not recommended for servo motor carrying a lot of load or torque, but for lightly loaded cables it will work. Using hot glue will require a little more effort when replacing a servo motor, but the glue can be separated from the servo housing with some effort.