You should script out your greetings, rehearse, and find a tone of voice that is reflective of your professionalism and your company’s personality. If applicable, your tone and your message should take into account that certain industries and companies are more conservative than others.
“Hi, thanks for calling the office of (insert your name). I’m away from my desk or out of the office. Please leave your name and number, and I’ll return your call as soon as possible. If you need immediate assistance, please hang up and reach our customer support team at (insert phone number). Thanks, and have a great day!”

Just like the importance of conducting yourself professionally in person and over email, you want to make sure that if an employer is trying to contact you, that they receive a professional greeting, even if you aren’t able to answer the phone right away.
The simple truth is that you need to be more aware of what you’re leaving for other people to hear. Sure, this doesn’t always register as a priority for users, but it’s never too late to reassess your greeting. a. Reading/Speaking in the Imperfect Tone: Tone is absolutely everything. Users don’t want to come off as being too nice, as it sounds insincere, or being too terse, as it can be interpreted as being rude. That being said, striking the right balance is absolutely essential. Your greeting exists as its own entity, and therefore, it should NOT rely on callers’ familiarity with you. Instead, it needs to appeal to the masses. As such, your inflection, i.e. the way you state your name and directions, needs to be both welcoming and firm. b. Injecting Humor & Insincerity: While humor/light heartedness can be welcoming, it can also convey a sense of informality, insincerity, and ultimately unprofessionalism. Why, because you’re not there to lend your humor or to contextualize. Instead, you’re assuming the caller has a working knowledge of your personality to ground the message. Though this might not sound like it’s all that terrible—it can be detrimental. As stated above, one should NEVER rely on a caller’s familiarity with you. Instead, aim to appeal to the masses. Humor is ultimately subjective, meaning not everyone has the same tastes; therefore, someone is bound to be turned off by a quirky or off-color remark. While implementing a light-hearted or even tongue and cheek tone can work, it’s just a really bad idea.