As I've been looking to fill a couple of key roles on my team recently, I've been sorting through dozens of inquiries and pitches, and reviewing stacks of resumes.

While some candidates do a good job of presenting themselves professionally in their cover note and resume, I am, to be frank, astounded by the number of candidates who still haven't even nailed the basics.

Here are five unprofessional things that some candidates do that ensure they will receive a rejection note from the company's HR department--or no response at all:

1. Writing an incomplete or poorly written cover letter.

Next to your resume, this is the most important first document you will be presenting to a recruiter. The cover letter tells the recruiter why you are interested in the role and why you believe you are qualified for it.

And yet, so many candidates send one or two-line cover emails along with their resume. Or, if they do decide to invest a few minutes to write something longer than just one or two sentences, it's unconvincing, and very often riddled with grammatical and spelling errors.

These "applications" get moved quickly into the "not interested" folder.

Pro tip: Write at least two or three paragraphs introducing yourself, explaining why you are interested in the company and the role being advertised, and why you believe you've got the right qualifications for the job.

2. Using an informal, or even flippant, tone in your cover letter.

I'm amused at the attempts some candidates make at trying to strike an informal tone in their very first communication with us. Some have even attemped to be flippant, or even humorous. Maybe that works with some recruiters, or at some companies, but it's a very risky strategy.

Pro tip: Don't try to be funny in your cover note. Stay professional.

3. Applying for a job when you have little or no relevant experience.

I'm amazed by the brazenness with which some candidates apply for roles for which they clearly have no demonstrated experience. For fresh graduates out of college or graduate school, this is to be expected. But for candidates who have been working in an industry and a function for at least a few years or more, suddenly applying for a role that has nothing to do with the work you've been doing for the past several years is, well, not going to work.

Pro tip: Even if you don't meet the minimum years of experience as outlined in the job description, at least have some experience that is directly relevant to the job. Otherwise, don't bother applying.

4. Failing to include a photo in your LinkedIn profile.

I could cite a number of flaws I've seen in LinkedIn profiles. Having a complete, up-to-date, well-written, and factually accurate LinkedIn profile is an absolute must for any candidate looking to get past the first screening for a role. But the mother of all mistakes has to be the lack of a profile photo, or an otherwise unprofessional shot that doesn't clearly show your face.

Pro tip: Invest in a professional headshot. If you're truly pressed for time or money, get a friend to take 50 shots of you in natural light and pick the best one of those.

5. Using multiple fonts and colors on your multi-page resume.

I recently received a resume that ran on for seven pages and was filled from top to bottom with information about the candidate in multi-colored fonts of varying sizes. It was dizzying to look at and impossible to read.

Pro tip: Keep your resumes short, and roughly in line with the standard format you see everyone else use. Use a limited number of font sizes, and stick entirely to black and white. Boring? Maybe. Will it land you an interview? Perhaps.