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In simple sentences. The Conditional Mood can be used in simple sentences beginning with "But for…" (But for the rain we should continue our way). It's also used in sentences with implied condition (I wouldn't waste my time on such things in your place). The mood is used by the speaker so as to sound polite (less straightforward) (I should like to speak to her).
In complex sentences. Real conditions.
Zero condition (General truth) – used with conjunctions "when, if, unless, provided". One action or result always follows another one (Oil floods if you pour it into water).
Type I – refers to the future (I will help you if you need my help; If I fall in love I will get married).
Unreal conditions.
Type II – the verbs in the oblique moods directly refer to the present or the future (If I could play the guitar, I would be in a rock band).
Type III – the action or the result refer to the past (If I had known of your arrival yesterday I should have met you).
Mixed (split) conditions – a) the present unreal condition and the past unreal result (If I were rich, I would have bought a big house a long time ago); b) the unreal condition refers to the past and the unreal action refers to the present (If he hadn't wasted so much time, he wouldn't be so nervous now).
