Sending in a CV which has incorrect spelling or grammar or which uses American spellings (if you are not in America).
Relying on the computer spell checker and not reading back over your work. This is very sloppy.
Not customising your CV to the role you are applying for.
Sending a paper copy of your CV when you have been asked to send it via email or vice versa. Always follow instructions.
Forgetting to include a covering letter with your contact details and those of the job you are applying for.
Making your CV overly long, but saying very little
Talking about your duties rather than your achievements
Leaving gaps in your employment history – this looks like you were unemployed. If that is the case, you should point out what you did instead (raised a family, voluntary work, travelling etc).
Using clichés and being vague
Adding the wrong contact details – check this several times as it is easy to get one digit wrong in your phone number.