Lashes can influence the personality of a look. I highly recommend them for any pro makeup application (unless it's meant to be specifically natural, perhaps for a period piece). Lashes open up the eye, give an "up and away" shape, instantly add glam, and provides focus to the eyes.
A pro makeup artist can help decide what lashes are appropriate- from a full strip to a few singles. Lashes should be measured and trimmed to custom fit your eye shape. Adhesives used are gentle and easy to remove; however one needs to steer clear of the usual adhesive if there's a latex allergy, and simply use an alternative.
If you're applying your own lashes, be sure to do your eye makeup and mascara first; otherwise you run the risk of disturbing the false lash. Do what you can to trim the strip lash down to the proper size if you are going that route. Try to get the lashes set down by the root of the natural lash line, against the eyelid (not on the lashes), but follow the lash line so you don't end up with the false lash lifting partway through wearing it.
Peruse the gallery below for inspiration...Cheers!