Causative Have And Get

Have

Have is a common causative verb. Instead of doing something ourselves, we "have" someone else do it instead. It has the following form:
The verb "to have" + object + past participle. For example:
- I had my jacket cleaned yesterday.
- Did you have your computer fixed?

Sometimes we use have as a causative verb when we intend to perform the action ourselves. For example:
- When will the report be ready? I'll do it by tomorrow morning.
- When will the report be ready? I'll have it done by tomorrow morning.

By using the causative the second sentence takes attention away from the doer of the action, and gives more attention to the action being done. It sounds polite and professional.

Get

Get is often used instead of have. For example:
- I got my computer fixed - I had my computer fixed. These two sentences mean the same thing.
- I got my jacket cleane. - I had my jacket cleaned. These two sentences mean the same thing.

Causative verbs are often used with negative experiences. In these situations it's more common to use have. For example:
- I had my wallet stolen. (I didn't actually cause my wallet to be stolen - someone stole my   wallet from me)
- She had her window smashed.

Source :

http://www.1-language.com/englishcourse/unit70_grammar.htm