[Raynor]

Now, the supreme being may sometimes intervene, directly or indirectly, but Tolkien always forces his characters to decide their own actions for themselves.

Well, there are some notable exceptions; concerning 'active intervention':

Originally Posted by The shadow of the past, FotR

- Behind that there was something else at work, beyond any design of the Ring-maker. I can put it no plainer than by saying that Bilbo was _meant_to find the Ring, and _not_ by its maker. In which case you also were _meant_to have it
...
- Why did it come to me? Why was I chosen?
- Such questions cannot be answered,’ said Gandalf. ‘You may be sure that it was not for any merit that others do not possess: not for power or wisdom, at any rate. But you have been chosen, and you must therefore use such strength and heart and wits as you have

Originally Posted by Three is a company

The Elves have their own labours and their own sorrows, and they are little concerned with the ways of hobbits, or of any other creatures upon earth. Our paths cross theirs seldom, by chance or purpose. In this meeting there may be more than chance; but the purpose is not clear to me, and I fear to say too much

Originally Posted by Council of Elrond

That is the purpose for which you are called hither. Called, I say. though I have not called you to me, strangers from distant lands. You have come and are here met, in this very nick of time, by chance as it may seem. Yet it is not so. Believe rather that it is so ordered that we, who sit here, and none others, must now find counsel for the peril of the world
...
At last with an effort he spoke, and wondered to hear his own words, as if some other will was using his small voice.
- I will take the Ring, he said, though I do not know the way.

Originally Posted by The breaking of the fellowship

- I wonder? said Aragorn. He is the Bearer, and the fate of the Burden is on him. I do not think that it is our part to drive him one way or the other. Nor do I think that we should succeed, if we tried. There are other powers at work far stronger.

[I also think that when foretelling is involved, it rules out free will to a certain extent; and some beings have a special doom ahead of them, such Earendil, Tuor, Thingol or Beren; Luthien is also moved by doom to Beren and their union is stated to part of the divine plan (cf letter #153)]