-ise or -ize in British English & American English?
It is generally true that the American preference for -ize is mirrored in British English by a general preference for -ise, so it is perhaps useful to standardise on one of these two patterns as far as possible. In a standard British dictionary - e.g. the Concise Oxford - you will often find that both options are possible in British English.
realise or realize
organsise or organize
Whilst for other entries -ize is listed as unmistakably American.
analyse = British English
analyze = American English
Those who have a preference for British English in this respect, for the sake of consistency can retain this preference for other spelling options, e.g.
programme, not program
colour, not color
metre, not meter
catalogue, not catalog
traveller, not traveler
When you are reading American English, it can be fun to spot the differences.