As per usual the Perseid meteor shower, which delivers more fireballs (magnitude -4 or brighter) than any other, is about to peak (technically predicted for 2000BST tonight, but that should be ignored).
Follow the assorted advice above; watch from after sunset tonight through till dawn tomorrow, sit back in a deckchair on the lowest rung or lie on something cosy on the ground so you can drink in as much of the sky as possible.
Unfortunately the recent full moon (rising around 2300BST) will hinder viewing somewhat this year. Activity in the UK will tend to appear to peak after moonrise, through till dawn. Try to shield yourself from the Moon ie sit in moonshadow; not only will meteors close to the Moon be ‘washed’ out but their paths will tend to be foreshortened anyway - the more spectacular trails will often be away from that part of the sky.
(above: green Perseid caught yesterday in skies over Japan, illustrating the dispersing smoke trail.)
Occasionally you may see other fainter, slower meteors from the concurrent Delta Aquarid-S and Alpha Capricornid showers (or just sporadics - there are typically several of those every night).
Note the Perseids actually last for weeks (it is just that it has a strong maximum for a few days, ie this weekend) and it would be worth looking tomorrow night into Monday morning as well if clouded out tonight (the main weather models ECM/GFS/WRF NMM suggest clear skies for most parts of the UK tonight and then cloud moving in late Sunday with only central/SE England tending to stay clear into Monday morning).
Added bonus: solar activity is picking up driven by a solar coronal hole. Worth glancing north on the off chance of aurora over the next 24 hours.