Here is a list of the biggest job search mistakes I see from people on LinkedIn, in no particular order:
Responding to job postings with "I'm interested - review my profile and contact me"
This is by far the most common response I see to jobs posted on LinkedIn, and I wonder how many recruiters actually take the time to review the profile of someone who posts that. Assuming you have no previous contact or relationship with the recruiter, THIS IS YOUR FIRST IMPRESSION! Would you send a resume with a cover letter that just says "I'm interested, here's my resume"? Hopefully not. The fact that you're interested in the job is great, but it does nothing to persuade the recruiter to be interested in you.
Ignoring application instructions
I think I've seen it all, and I'm sure you have too. There are people who ask how to apply even though it clearly says to visit their website, people who reply with "check out my profile and let me know if there's a fit" even though the ad says to email a resume, people who ask for the recruiter's email address even though it's in the ad, and on and on. The bottom line is this - if you're not following the instructions on how to apply, you're telling the recruiter that you don't know how to follow instructions.
Taking the lazy approach
Unfortunately there will always be people who want to take shortcuts, but when you're job searching you're just going to come across as lazy. I have people all the time who write to me and ask questions that can easily be answered by reading my profile or website. In fact, less than half of the people who contact me through LinkedIn about my service have even looked at my website, even though the URL is prominently displayed on my profile. Always, always, always review the recruiter's profile and read the entire job ad, if there is one, before initiating contact. Remember, you've only got one chance for a positive first impression.
The way you present yourself online is just as important as how you present yourself in an interview. Would you go into an interview and plead for a job because it's unfair how the world has treated you? No, jobs aren't offered to those who need it the most - they are offered to the most capable candidates. You need to show confidence online and in person so they can see the positive impact you would have on their business.
Using a resume and LinkedIn profile that don't match
I review hundreds of retail resumes every year and I regularly see LinkedIn profiles that don't match the resume - a sure-fire red flag for recruiters. If the job titles, dates, and company names on your profile are different than your resume, how do you expect to earn their trust? Not all the information needs to be exactly the same word for word, but make sure the core information is the same on both. (Dates are a common problem - make sure your dates are accurate and consistent on both your resume and profile.)
Not adding recommendations to profile
Written recommendations have always been a valuable tool in a job-seeker's toolbox, as they provide a third-party perspective that will be trusted much more than your own opinion of yourself. LinkedIn allows us to showcase these recommendations for each and every visitor who checks out our profile (we can also choose not to add it to our profile, if it's not a great recommendation). So why wait? Reach out to past, or possibly current, DMs, RMs, RVPs, peers, subordinates, etc. and get some recommendations on your profile. It's getting to the point where it's expected - if you don't have any, recruiters may wonder why.
Using LinkedIn to reply to job postings but nothing else
There's nothing wrong with applying to advertised job postings, but don't stop there - you could be doing more. The best method for finding the job you really want is to take a targeted approach by researching companies, identifying contacts, and reaching out on your own. Here's a 5-step guide that might help. While it certainly takes more effort and initiative, you can put yourself in the right position at the right time, before the opportunity gets put out to the masses. Also, don't forget third-party retail recruiters - get in their database so you'll be considered when something comes up.
Job searching involves much more than a resume and LinkedIn profile. It requires a strategy and you need to think about how you are going to access job opportunities, how you are going to network, who you want to network with, and how you want to present yourself through your online profile and communication. And remember, every comment you make on the internet is there for everyone to see. Don't assume no one's watching.
Best of luck!