Originally Posted by guest
(You mean to write where should I use 'will', and where should i use 'would' ? - "where to use ...." is a sentence fragment and not a question.)
"Will" is a modal used to indicate certainty.
I will not go.
I will be home in time for dinner.
Oxford will beat Cambridge in the next boat race."
Among the uses of "would" (also a modal) , and I think the one that you are looking for here, is to indicate the certainty of a result given a hypothetical situation that is in some way an alternative to the speaker's reality.
I wouldn't go if he wasn't paying
(reality: he is paying, and I'm going);
I would be home in time for dinner if it wasn't for the traffic.
(reality: because of the traffic I won't be home in time for dinner - at least that's what the speaker wants the listener to believe!);
Oxford would beat Cambridge if they would only train a little harder.(reality: Oxford has no hope because they spend too much time at the pub).
...just a quick something for you anyway...