Duration of 1 cycle = Time high + Time low

                                                                                                           1
Frequency of oscillation (pulse repetition frequency) =  ------------------------------
                                                                                         duration of 1 cycle

R is in Ohms, C is in Farads, time is in seconds, frequency is in Hertz.

Start with R1 and R2 the same value.

Try to use values between 10nF and 10uF for the capacitor, and between 1k and 1M for the resistors.

Since the 555 can produce large current surges, a 10uF capacitor should be connected directly between pins 1 and 8 of the IC, observing the polarity of the capacitor.
 

Using the loudspeaker, set the frequency to 1 kHz to make a tone generator, morse oscillator or simple organ.

Using the buzzer, set the frequency to 1 Hertz to get a pulsed alarm. This may, depending upon the type, need a diode as shown in the relay circuit

Use the relay circuit to be able to switch high power circuits that the 555 cannot handle directly.

Set the led frequency to 1 Hertz to make a dummy burglar alarm warning.