When you apply perfumes apply them to pulse points such as the folds in the crook of your elbow and back of knees, wrist, neck and cleavage. Make sure you do not rub wrists together as this crushes the smell. Spraying a little into the air is also good if you walk straight into the perfume. This helps to diffuse it over your body. Do not simply apply to the neck always work up the body as the scent rises. Also consider wearing in your bra a small ball of perfume impregnated cotton wool.
Consider layering perfumes. Use all the same perfume in various products. Begin with shower or bath gel and then rub in body lotion or spray with a matching after bath spray. Finally apply the scent preferably as perfume or EDP. I find that the use of body lotion makes you feel really scented and it is probably to do with starting at the feet and applying the scent all over allowing the scent to rise. It also makes you feel extra special and very pampered.
Keep bottles tightly stopped, away from direct heat and out of sunlight. You will certainly know when they have gone off as you'll notice that you do not get that lovely boost of heavenly scent when you spray or dab and the fragrance will look darker in the bottle. Some perfumes come in blue or opaque bottles and these store perfume well. http://www.fashion-era.com/perfume_history.htm