When you've been at a job for quite some time, you might inevitably reach the point when you're ready to quit. Maybe you're unhappy with your salary and think you can do better elsewhere. Maybe your boss is unreasonable, or your company culture isn't one that aligns with your personality.

No matter the reason for leaving your job, it's important to do so on the most professional note possible. Why? You never know when you might need someone from that company to serve as a reference, and if you wreck your relationships on the way out, it could hurt your career in the long run. With that in mind, here are a few major mistakes to steer clear of when resigning from any given position -- no matter how bad things happen to be.

Woman packing up a desk

Image source: Getty Images.

1. Leaving without adequate notice

In most industries, two weeks is the standard amount of notice workers should give for leaving their jobs. Unless you're certain your field operates under an exception, be sure to give a full two weeks' notice when leaving your company. While your employer probably won't manage to find, hire, and onboard a replacement for you during that time, you'll at least be giving your manager a jump-start, and that's something that will work to your advantage if you ever need to call in a favor down the line.

2. Telling your colleagues before your boss

If you're friends with your coworkers, you may be tempted to share the news that you're leaving your job with them before sitting down to tell your boss. Don't do it. A good way to look completely unprofessional is to have your manager hear through the office grapevine that you're planning your departure, so avoid spilling the beans until you've conveyed that message to your boss directly. Along these lines, it's wise to ask your manager how he or she wants to go about sharing the news. Your boss might request that you keep things under wraps for a certain amount of time -- say, so that they can discuss it with higher-ups or make plans to inform your team all at once. And if that's the case, it pays to be respectful of that request.

3. Writing a nasty resignation letter

Even if you're planning to inform your boss that you're quitting face to face, it's still a good idea to compose an official resignation letter to go along with that news. But don't use that letter as an opportunity to air the various grievances you've been harboring. Doing so will only leave a bad taste in your manager's mouth and make you look petty. Rather, keep your note polite and to the point. Let your boss know when your last day will be, thank your manager for the opportunity, and leave things at that.

4. Offering no help with the transition

When you're in that final two-week period at work and are eagerly anticipating your departure, you may be inclined to let your remaining responsibilities fall by the wayside. But that transition period isn't the time to be lazy. Chances are, you're leaving some otherwise decent people in the lurch by resigning, whether intentionally or not, so if anything, you should be going out of your way to make things easier for those impacted by the change. Making an effort to aid your company during your final days as an employee will only help solidify the good reputation you should be aiming to leave with, so don't skip out early or let paperwork pile up when you know you can do better.

There's nothing wrong with quitting your job when it makes you unhappy or a better opportunity comes your way. Just don't make the mistake of leaving on a negative note. While telling your manager to take that job and shove it might make you feel good in the moment, you're more likely than not to regret that behavior in the long run.

The Motley Fool has a disclosure policy.