It's a valuable networking tool, helping professionals connect for jobs and advice. But many LinkedIn members aren't taking full advantage of the networking features of the site. When used to its fullest, LinkedIn can be an even more powerful social media tool than Facebook and Twitter.

Setting up your LinkedIn profile is only the beginning. Here are a few mistakes you may be making on LinkedIn that could cost you important business connections. By knowing about these mistakes, you can make your profile more powerful and reach more of your industry peers on the site.

1. Not completing your profile 

When LinkedIn members look at your profile, what do they see? Is your entire career outlined in your profile or just your current position? Do you have a current photo that would help your peers locate you at a networking event or conference? Your LinkedIn profile should give a full overview of your experience, including as much background as possible. A position you held early in your career could connect you with a colleague from those days who could benefit your business now.

2. Failing to join groups

LinkedIn offers Groups as a way for members to find other people within their industries or areas of interests. These groups are a great way to share ideas and troubleshoot issues, but at their core, they offer a way to network with other business owners. LinkedIn occasionally suggests groups you may like, but you can also browse the directory or search for a group using the search box at the top of each page.

3. Not endorsing others 

Endorsements are an easy way to let your colleagues know you support them. You simply endorse other professionals for specific skills you know they have under the Skills & Endorsements section of each person's profile. Not only will that person be notified of your endorsement, your picture and name will appear next to that skill under the person's profile as having endorsed him. You can also write recommendations for colleagues who have worked with you in the past.

4. Failure to connect

You can create a LinkedIn profile, but without connections you're missing out on the "networking" part of the site. Start by connecting with people who are in your professional circles and expand from there, adding past colleagues, others within your industry, and people you meet while networking in groups on the site. You'll see your connections' updates on your newsfeed and be alerted when they change jobs or celebrate a work anniversary. Be sure to congratulate them when you see these items to keep your name fresh on their minds.

5. All take, no give 

As with other social media sites, one of the top mistakes professionals make is in only posting when they need something. If you're inactive most of the time, only using the site to ask a colleague for a favor or to market something, you'll likely be disappointed by the results. Make an effort to interact by posting links to useful articles and commenting on other people's posts on your newsfeed. Then when you do post about your exciting new product or upcoming event, you'll find that others are more willing to support you.

6. Unprofessionalism

While it may be a social networking site, it's important to remember at all times that LinkedIn is a professional social networking site. Your profile picture should capture your spirit while still being professional, whether it's a shot of you at your favorite coffee shop or a standard business headshot. Every word on your profile should be grammatically correct and typo-free, even if it means asking a friend or colleague to proofread it. Most importantly, when you post status updates or comment in groups, every post should represent your brand in the best light possible. Resist the urge to engage in arguments with those who are inciting drama by always keeping in mind that others could be judging you by your comments.

LinkedIn is an important networking tool for every professional. The site has many tools designed to help you connect with those you've worked with in the past and suggesting those you can work with in the future. When used correctly, it can help you bring in new business and get the support you need as you grow your company.