Your CV is often your first introduction to a company or to a recruitment consultant.   How far do you think the application will go if there are spelling mistakes and grammatical errors contained within it?   So the first thing is pay attention to detail.

The presentation of the CV is important too.   It should have clearly defined sections such as personal details, education and training, work experience, key skills and achievements etc.  

Try to keep the CV concise and aim for no more than two to three pages in length.

Commence the employment history with the latest position and work backwards, putting dates of starting and leaving each role.    Explain any gaps in employment history.

Whilst not essential, it is useful to show hobbies and interests at the back of the CV as this can show the employer some useful information about your personality.

Remember that the CV is like a sales document.  You are trying to get the employer interested in you otherwise you won't be getting to interview stage.