When a San Diego public relations firm posted a job for a fall intern last year, resumes poured in from all over southern California. Managing partner Cathy Sperrazzo estimates she interviewed a dozen candidates from three different universities, all of them bright, motivated and eager to gain experience in the communications industry.

Yet only one candidate followed up with a thank-you note.

It was a surprise and disappointment to Sperrazzo, who has required her own children to write thank-you letters since they could pick up a pencil. She ultimately hired the student who sent a note, despite the fact that she was a year behind many of her competitors, because Sperrazzo felt the simple act showed an added layer of commitment to the job.

Always considered a sign of good manners, the thank-you note remains an important and powerful tool in today’s business world. But in the age of texts and emails, figuring out the best way to follow up after an interview or noteworthy meeting can be confusing. While a stamped handwritten note on engraved stationery was once the gold standard for showing gratitude, now many other options abound, from email to social networking to even phone texts.

Most etiquette experts and executives agree that a follow-up message within 24 hours of an interview is an essential part of clinching a job offer or promotion. While handwritten notes are appreciated and even singled out, sending a note via electronic mail is also widely accepted among hiring managers and other executives these days.

“Emails are perfectly 100 percent okay to send,” says Tina Fox, metro market manager for Accountemps, a Robert Half Co., and a 16-year veteran of the staffing and executive search industry.

Anna Redmond, an author and online entrepreneur, also favors the electronic format when it comes to showing gratitude.

"I run a startup, and in my space I would definitely go with the email," notes Redmond, co-founder of Hippo Reads, an online media venture that helps academics go mainstream. "It's faster and it's what is expected."

A 2012 survey of 500 hiring managers by Accountemps found that 87 percent believe email is an appropriate way to express thanks after a meeting. Phone calls were also deemed acceptable by 81 percent of the surveyed managers, although phone texts were soundly rejected, with only 10 percent approving of this method.

Expressing thanks via social networking sites like LinkedIn or Facebook is also often acceptable, Fox notes, especially when a company is immersed in new technology or it is the interviewer's preferred method of communication.

As the electronic thank-you note becomes the norm, however, there are some important rules that its supporters should keep in mind, experts say.

Avoid sending out a bulk email to a group, for instance, warns executive search consultant Kristian Schwartz. "It's just lazy, period," he says, noting that it's best to individually acknowledge everyone involved in the interview, from the recruiter to the administrative staff.

Also, keep it short and sweet. "There's no need to send a regurgitated version of your resume in an email," Schwartz says.

While Schwartz isn't a big fan of postmarked thank-you notes, he acknowledges that they are a way to stand out among the pile of in-box notes. He suggests sending both emailed and handwritten notes as an extra way to get noticed. Since office mail systems have changed and diminished over the last decade, that covers all bases in case the mailed note arrives several days later, he says.

"I, for one, check my work mailbox every two weeks. It's a bit of a dinosaur," Schwartz points out.

Others agree that the power of penned letters shouldn't be underestimated. Accountemps' Fox recalls a recent example in which an administrative assistant brought her a handwritten thank-you note from a candidate she had interviewed only an hour earlier. The candidate had left her office and immediately penned a note, then returned to the building to hand-deliver it to her office.

"To me that really resonated personally, and showed me [the candidate] could think outside the box," she said.

Yet in the end, most agree it's substance over form that ultimately wins over the boss.

"It's what you say in the email or the thank-you note," Redmond stresses, "not how lovely your penmanship is, that gets attention."