Look for flowers that are not yet fully developed. Most cut flowers, with the exception of some tropical flowers and fresh orchids, will continue to open after they’ve been put into the vase. A flower bud should be just slightly open–this is a general rule of thumb. There are some new rose varieties that have that full-blown look right from the beginning and stay like that for over a week, but these are an exception. If you’re not sure if a rose is fresh, lightly squeeze the rose with your finger tips and see if there is some substance there. If it feels full, and not to soft, it should last for over a week.
Blooms should be firm and blemish free (unlike the “bruised pedals” below!)
Foliage should be crisp and green, not yellowing or becoming mushy (shown below)
Check the bottom of the stem. If the bottom of the stem is discolored, it usually is an indication that the flower is old or has been out of water for too long.