To begin with, we created an empty game object. With the empty selected, we opened the component menue and assigned the object an 'Ellipsoid Particle Emitter,' a 'Particle Animator,' and a 'Particle Renderer.' In the materials menu under the Particle renderer, we selected the fairy dust element. This creates a rather generic white particle system which is useful as a starting point for experimentation. Under the particle emitter settings, the maximum and minimum size of the particles can be altered, as well as the x, y and z coordinates of the elliptical cloud which is generated. The minimum and maximum energy determines the duration of each particle before it fades away. By adding a 'World Force,' which creates a force that determines which way the particles are pushed no an axis when spawning, can be used to create an upward motion like for example fire. To add further realism, the random axis option pushes some particles slightly off axis, giving the particle effect a more natural body. If we wanted to apply this effect to say; a jetpack, the local velocity causes particles to act in relation to a parented object.
the 'Tangent Velocity' option, pushes the particles out on an axis, creating possibly an explosion effect. To add even further realism, the 'Angular Velocity' settings can be sued to add rotation to the particles, again making them seem more natural. Also, using the particle animator, you have the option of making the particles fade through a range of colours during their lifespan. By adding a red to yellow gradient, an effective flame illusion can be created. Bellow is a particle system showing fire embers which I created while experimenting in unity. It gives an idea of a particle system can be manipulated to achieve hopefully realistic results: