Well, I can only really do it by example, and there are times when either would do. But here goes:

'How can I get the room warm?'
'It's not difficult: try lighting the fire.'

'What can I do to help?'
'Well I haven't any matches, but you could try to light the fire with a spill.'

I think it's something to do with whether the verb 'light' is the main point of the action - to warm the room - or the verb 'try' - because the fire mightn't light after all.

Works for 'try to chop'/'try chopping' down the tree, I think. Does it work for other verbs than 'try' though, I wonder?

Emma

From the Internet (Fowler's is in the other room and I can't be bothered to fetch it) ...

Here is a brief review of the differences between gerunds and infinitives. Gerunds are formed with ING: walking, talking, thinking, listening Infinitives are formed with TO: to walk, to talk, to think, to listen Both gerunds and infinitives can be the subject of a sentence: Writing in English is difficult. To write in English is difficult. Both gerunds and infinitives can be the object of a verb: I like writing in English. I like to write in English. Only gerunds can be the object of a preposition: We are talking about writing in English. It is often difficult to know when to use a gerund and when to use an infinitive. These guidelines may help you: Gerunds are often used when actions are real, concrete or completed:: I stopped smoking. (The smoking was real and happened until I stopped.) Infinitives are often used when actions are unreal, abstract, or future: I stopped to smoke. (I was doing something else, and I stopped; the smoking had not happened yet.)

So "Try to light the fire" sounds like a general instruction in a scouting manual, referring to fires in general. "Try lighting the fire" refers to that fire there, in front of you.

That's my guess, anyway.

Yes, that make sense: 'try to light the fire' is future/unreal and the fire may not light. Which is also why the distinction works with verbs like 'try' but not all verbs.

Emma