Come into the salon with a crystal-clear idea or better yet—a visual (or three)—of the color and tone you’re hoping to achieve rather than a vague description. Your idea of "ashy" or "honey" blonde could be vastly different from your stylist’s and things can easily get lost in translation; a photo leaves little room for misinterpretation.
On that note, when searching for photos to bring in, try to look for examples of people who have similar skin tones (and eye colors) as you do. This will ensure that you end up with a color that flatters your complexion, rather than washes you out or looks super unnatural.
Oropeza also advises that you always ask your stylist, "What can we realistically do in one day?" Again, depending on how dark your hair is and how much you want to lighten it, it can take several appointments to reach your desired shade. "It’s better to go lighter in a few stages to maintain the health of your hair than to blast it with bleach all at once." (True story: I made the mistake of going blonde in one appointment and ended up with broken spikes of hair in the back of my head that took months to grow out evenly.)
A final note: "Blonde hair requires more maintenance than brown, so make sure to ask how often you’re going to have to come in for touch-ups before you commit," says Oropeza. (Translation: Going and staying blonde will require some budgeting.)