This is a big question!
I write CVs professionally - would post my link here but I don't think that's allowed?
Sections:
Heading - name
Contact details - address, email, phone
Summary - short, bulleted, two or three sentences - why you're perfect for the job - specific relevant skills and experience
Work experience - job title, organisation, location, dates (months and years), then a few bullets about your main responsibilities and achievements. Quantify using numbers and names wherever possible. Most importantly - keep this section succinct and totally relevant to the job you're applying for.
Education, training and other skills - list only your most relevant and impressive stuff here. Include languages, degrees, professional affiliations and memberships, certifications, voluntary work (which can also be listed in the work section above)
References - just put 'references are of course available on request'
Tips:
List work, study etc reverse chronologically
Leave lots of white space so it's easy to skim read
Use a modern simple font (I like century gothic)
Keep to two pages (cliche but true)
Get someone else to proof read it for you before sending
MOST IMPORTANTLY - Keep all the content completely relevant to the specific job - use all the info you have available, include all the points mentioned in adverts / job descriptions / person specifications. Imagine you're the employer and write the perfect candidate CV - as best you can.