If you have borrowed equipment from a friend or have just bought it new, don’t use it the very first time on an important assignment. One, your hands are not set on the equipment yet, your attention will be diverted on the proper functioning of it rather than the actual shoot. And secondly, though very rare to happen, new equipment bought officially or from grey market, may have a manufacturing defect, which may come to your notice as you shoot or later as you transfer your images to the computer. If it is a film camera, only when the rolls are developed and returned!!! Too late!! Never forget the booklet, if you cant find a function, you certainly will need to refer to the manual. Bookmark the important areas of the manual for quick reference. Don’t refer to the manual in the presence of your client or support team, as psychologically it will dilute their confidence in you. However, do so rather than doing something wrong if you can’t avoid it