it costs a bit more but instead of buying eau de toilette, buy eau de parfum. It has a stronger concentration and thus lasts longer. You need less, so you pay more, but the bottle will last longer too. There are also several ingredients that stay on your skin longer. like light citrus smells will loose themselfs faster than a parfum with sandal wood or patchuli. buy a small spray dispenser, you can get them at most stores. You fill it up like a lighter and they are very practical to carry in your purse to reapply in the afternoon. Apply where you can feel a pulse: behind the ears/side of the neck, on your wrist. and between your breasts. It's important not to rub (the way many of us do when applying to the wrists) just tap it. Also using the scented body lotion of the same parfum will help. The oils in the cream somehow makes it last longer. I have heard about vaseline, but I don't like to use it because it is so exremely greasy.
Honestly I think it depends on the perfume. If I wear a cheaper perfume the smell goes away fast. But if I wear an expensive strong scenting perfume, the smell lasts so much longer, and I can even smell it on my clothes the next day. For example, I have a Victoria Secret perfume that I spray but I feel like the scent is not that strong so it fades and the smell doesn't last long, but when I wear my Versace Bright Crystal perfume (which smells amazing by the way) the smell doesn't seem to fade, it lasts for a long time and I got a lot of compliments on it too. I think it depends on how strong the scent is.
First rub a little Vaseline over the spot where you're spraying the perfume. Then spray the perfume onto the Vaseline. The perfume should get trapped in the Vaseline and stay for hours.
Spray it behind your ears, neck and well... umm... it may sound pretty weird but applying it between your breasts makes it last longer too. Also, after spraying it on various body areas, apply a little vaseline.