なさる is a 尊敬語（そんけいご） (honorific speech) verb which acknowledges and respects the actions of another (never the speaker). Like
お～になる,
なさる has exactly the same meaning as
する.
なさる can be utilized in any situation where
する would be used, as a direct replacement. It is a special-class verb, which means that it has some unique conjugation rules. In its casual form, it will conjugate in exactly the same way as a
う-Verb.
-
週末（しゅうまつ）もお仕事（しごと）をなさるのですか。
Are you going to work over the weekend also?
-
勘違（かんちが）いなさらないで下さい。
Please don't take this the wrong way.
-
社長（しゃちょう）は先週（せんしゅう）どちらでゴルフをなさったのですか。
Boss, where did you go to play golf last week?
-
納得（なっとく）なさらないなら私（わたし）に言（い）ってください。
If you are not with me on this, please let me know.
However, in the polite form, instead of る changing to り (as would be expected of a
う-Verb), it will change to い instead.
-
お飲（の）み物（もの）はどうなさいますか？
What would you like to drink?
-
忘（わす）れ物（もの）はなさいませんか。
Did you forget anything?
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お客様（きゃくさま）、どうなさいましたか。
Valued guest, what seems to be the issue?
-
彼（かれ）は計画（けいかく）を変（か）えることはなさいませんでした。
He did not do anything to change the plan.
Although some Japanese speakers will use it, expressions like
なさっていらっしゃる are considered double keigo (
なさる is 尊敬語（そんけいご）, and
いらっしゃる is also 尊敬語（そんけいご）), and are technically incorrect. However,
なさる may be partnered with ます, which is simply 丁寧語（ていねいご） (polite speech).
-
社長（しゃちょう）は今（いま）、ゴルフをなさっていらっしゃる。
The CEO is currently playing golf quite playingly. (Unnatural Japanese, with unnatural English to match!)
-
社長（しゃちょう）は今（いま）ゴルフをなさっています。
The CEO is currently playing golf. (Natural Japanese)
なさる is considered a little bit old fashioned in modern Japanese, and お～になる is the preferred form used by most native speakers.