This script was designed for a decent balance of efficiency and usability. It is good if you know what you wish to accomplish, and avoids added complexity of some of the other wrappers. The actual function is 46 lines long.
If you look closely, you'll see that all this script really is is an llParticleSystem with all the parameters, commented.
// Keknehv's Particle Script v1.2
// 1.0 -- 5/30/05
// 1.1 -- 6/17/05
// 1.2 -- 9/22/05 (Forgot PSYS_SRC_MAX_AGE)
// This script may be used in anything you choose, including and not limited to commercial products.
// Just copy the MakeParticles() function; it will function without any other variables in a different script
// ( You can, of course, rename MakeParticles() to something else, such as StartFlames() )
// This script is basically an llParticleSystem() call with comments and formatting. Change any of the values
// that are listed second to change that portion. Also, it is equipped with a touch-activated off button,
// for when your particles go haywire and cause everyone to start yelling at you.
// Contact Keknehv Psaltery if you have questions or comments.
MakeParticles() //This is the function that actually starts the particle system.
PSYS_PART_FLAGS , 0 //Comment out any of the following masks to deactivate them
//| PSYS_PART_BOUNCE_MASK //Bounce on object's z-axis
//| PSYS_PART_WIND_MASK //Particles are moved by wind
| PSYS_PART_INTERP_COLOR_MASK //Colors fade from start to end
| PSYS_PART_INTERP_SCALE_MASK //Scale fades from beginning to end
| PSYS_PART_FOLLOW_SRC_MASK //Particles follow the emitter
| PSYS_PART_FOLLOW_VELOCITY_MASK //Particles are created at the velocity of the emitter
//| PSYS_PART_TARGET_POS_MASK //Particles follow the target
| PSYS_PART_EMISSIVE_MASK //Particles are self-lit (glow)
//| PSYS_PART_TARGET_LINEAR_MASK //Undocumented--Sends particles in straight line?
//PSYS_SRC_TARGET_KEY , NULL_KEY, //Key of the target for the particles to head towards
//This one is particularly finicky, so be careful.
//Choose one of these as a pattern:
//PSYS_SRC_PATTERN_DROP Particles start at emitter with no velocity
//PSYS_SRC_PATTERN_EXPLODE Particles explode from the emitter
//PSYS_SRC_PATTERN_ANGLE Particles are emitted in a 2-D angle
//PSYS_SRC_PATTERN_ANGLE_CONE Particles are emitted in a 3-D cone
//PSYS_SRC_PATTERN_ANGLE_CONE_EMPTY Particles are emitted everywhere except for a 3-D cone
,PSYS_SRC_TEXTURE, "" //UUID of the desired particle texture, or inventory name
,PSYS_SRC_MAX_AGE, 0.0 //Time, in seconds, for particles to be emitted. 0 = forever
,PSYS_PART_MAX_AGE, 1.0 //Lifetime, in seconds, that a particle lasts
,PSYS_SRC_BURST_RATE, 0.02 //How long, in seconds, between each emission
,PSYS_SRC_BURST_PART_COUNT, 2 //Number of particles per emission
,PSYS_SRC_BURST_RADIUS, 5.0 //Radius of emission
,PSYS_SRC_BURST_SPEED_MIN, 5.5 //Minimum speed of an emitted particle
,PSYS_SRC_BURST_SPEED_MAX, 6.0 //Maximum speed of an emitted particle
,PSYS_SRC_ACCEL, <0.0,0.0,-0.8> //Acceleration of particles each second
,PSYS_PART_START_COLOR, <0.0,0.0,1.0> //Starting RGB color
,PSYS_PART_END_COLOR, <0.6,0.6,1.0> //Ending RGB color, if INTERP_COLOR_MASK is on
,PSYS_PART_START_ALPHA, 0.9 //Starting transparency, 1 is opaque, 0 is transparent.
,PSYS_PART_END_ALPHA, 0.0 //Ending transparency
,PSYS_PART_START_SCALE, <2.4,2.4,0.0> //Starting particle size
,PSYS_PART_END_SCALE, <1.3,2.3,0.0> //Ending particle size, if INTERP_SCALE_MASK is on
,PSYS_SRC_ANGLE_BEGIN, PI //Inner angle for ANGLE patterns
,PSYS_SRC_ANGLE_END, PI //Outer angle for ANGLE patterns
,PSYS_SRC_OMEGA, <0.0,0.0,0.0> //Rotation of ANGLE patterns, similar to llTargetOmega()
MakeParticles(); //Start making particles
touch_start( integer num ) //Turn particles off when touched
state off; //Switch to the off state
llParticleSystem(); //Stop making particles
touch_start( integer num ) //Turn particles back on when touched