Never submit your form uncompleted or blank with a "Refer to enclosed CV" note. This will eliminate your application straightway! The employer has his / her reasons for recruiting by application form rather than CVs, and you must follow procedures if you wish to be short-listed.
Some employers do not mind if you submit a CV in addition to the form. Make sure there is clear option to do this by either seeing it on the advertisement or contacting the employer directly.
Never send additional information such as supporting statements unless the employer specifically requests them. If you are required to send evidence of professional training, educational history or copies of references, never send the originals. Photocopy them and only produce originals when specifically requested to do so.
In the event that you are given the option to submit additional pages or supporting statements with your form, follow instructions on how to tag these, stating your name, job reference number and page number.
Never leave blank spaces on the application form when you are required to complete all sections. On some application forms, sections might not relate to you, such as whether or not you are a refugee, or eligible to work in the United Kingdom. In circumstances such as these, simply write or type "Not Applicable". Otherwise, answer all other sections as required.
Particularly for those applying directly online on employers' websites, never alter the size or format of the employer's form unless you are clearly given that option. For international corporations such as the United Nations, you are limited to writing a certain number of characters and you will not be allowed to contravene procedures. With other types of forms, the sections have varying columns, indicating the amount of information you might be required to supply.