I have a wide range of interests, but am mostly likely to contribute to articles relating to British culture, science, history, cuisine, arts and philosophy. I'm a scientific sceptic, so I'm critical of pseudo-scientific articles with no evidence or sources. I'm also a proponent of Proper English, so encourage British and Commonwealth spelling where appropriate (it is used in more countries after all).
I've started a few articles but am primarily a proof-reader - when I see an article on Wikipedia that's misspelt or contains insufficient details or wooly thinking, I tend to correct it. Or, if I look up an article and it doesn't exist, I'll create it and hope someone else fleshes out the details.