will in if-clauses

When the situation or action depicted in the if-clause is a result of the main clause, the will future is used in the if-clause.
He'll pay me $10 if I'll help him do the dishes.
(Doing the dishes is the result of paying ten dollars.)

would in if-clauses

In polite requests would is possible in if-clauses.
It would be nice if you would help me in the kitchen.
(Are you ready to help me in the kitchen?)