The best advice I can give is really listen to the sound you are trying to achieve and check out as many different effects and combinations of effects as you can.

There are broadly speaking, 6 types of effect.

Overdrive and Distortion – overdrive simulates the effect of an overdriven tube amplifier. Distortion produces harder, metallic distortion with many upper harmonics.

Delay/Echo – samples the original signal and plays it back slightly later, simulating natural echo. Makes a delay sound measured by length of delay in milliseconds and the number of repeats. Gives variety of sounds for different styles.

Modulation Devices – this includes chorus, flanger, phaser and tremolo. Chorus combines a slightly delayed signal, with the original signal and modulates it to create a thick shimmering choral sound. à la The Police.

Flanger – electronically creates a slight delay and combines it with the original signal to add a swirling doubled effect.

Phaser – combines an out-of-phase signal with the original signal, for a sound similar to that of a rotary speaker. à la Electric Ladyland by Jimi Hendrix.

Tremolo – varies the volume of the signal for a pulsating effect as found on vintage amps e.g. Vox AC30.

Changing Tonality of Sound Devices – EQ boosts or cuts a particular frequency band for flexible control of tonality. Wah produces a distinctive ‘WAH WAH’ effect by boosting/cutting a specific frequency range à la Voodoo Child by Jimi Hendrix

Compression – produces a level dynamic thus improving sustain and giving a studio sound. Possibly the most important effect of all.

Pitch Shift – shifts the pitch of the original sound to various intervals à la Brian May.

You can then buy these effects as individual units or as a combined multi effect.

There is now a big movement back to individual effects that are much simpler to use and allow a personalised custom set-up.