Crush a piece of the pileus to intensify the odour, which may also be stronger when the fruit-body is warmed (such as after being carried in a container in your pocket).
Human scent receptors are rapidly saturated, and odour can seem to disappear (the ability to smell the odour will come back after a while). Some odours are difficult to characterise, but the range of options provided here covers most odours that will be encountered among agarics. Some odours are pleasant when faint, but unpleasant when strong, and some of the categories grade into one another (choose more than one option if unsure).
An example is Entoloma aromaticum, which has an odour like feijoa, or some types of boiled sweets. Another example is Lepista nuda which has a pleasant, strongly aromatic odour.