Q: What is the best software fo cleaning up MacBook Air?

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If you can avoid using them, it's much better for you and for your data. Cleaning apps have got the "ability" to delete system files and damage Mac OS X, so you shouldn't install any of that type of applications

As already stated by mende1  these type os Utiliies are not recommended and indeed not necessary.

Mac OS X tends to look after itself.

Read Here  > https://discussions.apple.com/thread/4545776?tstart=0

https://discussions.apple.com/message/20969069

To keep your Mac Happy... See Here...

http://support.apple.com/kb/HT1147

The Safe Mac  >  http://www.thesafemac.com/mmg/

More Info Here  >  The myth of the dirty Mac

You are welcome