Go to the Edit menu at the top of your EndNote library, and choose preferences on the drop-down list to customise the features and look of your EndNote library.
Below are a few of the preference options that can be used...
Change case - This can be useful if you do not want EndNote to override the capitalisation of certain words; such as acronyms, proper nouns and equations. Create a 'Do not change the case of the following items' list in your EndNote preferences
Display Fields - What information do you want to see when your EndNote Library opens - Author, Journal, Title...Use this preference to choose which fields are displayed. For more information on display fields and editing your EndNote Library see the Sort and edit your EndNote References page
Duplicates - EndNote's default is to identify duplicates as references of the same reference type with matching Author, Year and Title fields. You can select to be more or less specific in searching for duplicates by clicking the check boxes to the left of the field name. For example, the criteria for identifying duplicates may need to be changed to pickup "Articles in Press" as opposed to published articles.
When choosing your Display Fields it maybe useful to display the record number
The Record Number is a unique number given to each reference in your library
Record Numbers are never repeated - even if the reference is deleted from an EndNote Library
Sorting your EndNote Library by Record Number can sometime be the only way to determine which record was entered first and which was entered last (especially if you have a large EndNote Library)
If need be, you can always return your preferences to the EndNote Defaults, or revert back to when the preference was last saved
Unless you need two versions of a reference, regularly check for duplicates and remove them from your library.