The conditional type 2

Type two:

If + past simple --------> present conditional.  If I saw him today / tomorrow, I would speak to him.

Main clause:

Present conditional / if clause: past simple.
Hypothetical and unreal conditions ( Present or Future reference).

The first case : 

The action is improbable / unlikely / doubtful.
_ You results would be better if you worked harder. ( Unread past = I don't think you will work harder)
_ If we missed our bus, we should have to walk ( I don't think we will miss it )
a) There is no difference as regards time. They both refer to Present ( now ) or Future ( tomorrow ).
_They never refer to the past.
b) But there is a difference in the degree of probability = type one is more probable than type two.

Type one: 

The action may happen or will probably happen.

1. - type two : The action might happen.

The second case:

The action is unreal / imaginary / hypothetical / dream.

1. _ If I knew how it worked, I would tell you what to do.
2. _ If I knew her house, I would tell you. ( But I don't know her house ).

Note: here that the past form is used here to indicate present unreality.
Note: the verb to be becomes were in all persons ( was is possible, but it is considered as substandard below standard - not good enough).

1. - If I were in your shoes, I would do it at one time.
2. - If it were raining, I'd take an umbrella.

# With inversion we drop If ( formal style ).
# Were I in shoes, I 'd do it at once.
# Was is impossible with inversion.