There has been a lot of conversation around careers and jobs lately (perhaps due to the recent Soft Skillz presentations, and because a friend is changing jobs right now).
You should manage your job change in a proactive and healthy way. Always negotiate a start date that works for you, and supports a fair and clean exit from your current employer.
ALWAYS give at least two weeks notice. But, take into account any project milestones or events that are close to your exit date, and adjust for those. It is up to your current employer to decide if they don't need you for those two weeks. I have experience where some will ask politely for you to leave that day, others choose to work out a transition plan for those two weeks.
When you do resign, bring a transition plan with you. The plan should cover what tasks, responsibilities and projects you are working on, who those should transition to (in your opinion), and how you plan on doing the transition. The higher level or more important your role is in the company, the more thorough your plan should be.
If you leave your soon-to-be ex-employer in the lurch, that will come back and bite you at some point. NEVER burn a bridge, unless you are playing Command & Conquer. Doing so will hurt your credibility and haunt you forever. Even if you hated the job, and it was super painful. Always leave gracefully.
On the flipside, you may get pressure from your new shiny employer to start sooner than you should or are comfortable with. This is a huge red flag. The good ones might ask, but will drop it when you explain your transition plan. The bad ones will threaten, cajole, throw a tantrum, etc.
If you have to, remind that them that they would not want to be left in the same lurch if someone was leaving their employ. Remind them (thanks Mel!) that they wanted to hire a professional, right? This is a sign that they are hiring a body, and not YOU.
If the transition isn't going to work out, it is better to back out of the new job before you start, than it is to either quite a week after you start, or be miserable in your new job for a year or two.
So that brings us to Job Hopping.
Don't do it. You need to actively manage your career. That means you need to have a plan, and think a few steps ahead. NEVER take a job because it is more money. I know that it is hard to say no to a lot of money. If it is really early in your career, then you might be able to jump for money once or twice.
If your new employer figures out you will jump to them for money, they know that you will leave them for money as well. This hurts your credibility and loyalty in their eyes. I have had staff, in the past, that I would not put in leadership positions, or promote, because of how focused on money they were coming in. I gave those people time to prove themselves before I committed more resources than I was willing to lose in a transition.
Try to stay at each job a minimum of two years, and have at least a five year term in there once in a while. It shows you know how to pick a good job, and how to have an impact with a company, beyond that initial project. A short term job will look like you are damaged goods. For example:
1. You can't finish what you start,
2. You don't know how to work in a professional/corporate environment.
3. You like to chase money/rank.
4. You haven't learned to work with people and on a team.
5. You don't read Brian's blog.
You should have a good reason and story for making every job change (regardless of how long you were there), especially the short jobs. This story should not be "I hated my boss." It should show that you had foresight and were progressively managing your career for growth.
The problem with a short job on your resume is that you might not get a chance to explain your decision. With a stack of reasonably qualified people, an employer would likely skip over people with jumpy job records. The employer will not want to invest the money it takes to recruit, on-board, train, and promote someone who is just going to leave in a six months or a year.
You need to look at where you are, where you want to be, and work out a timeframe. Perhaps the right time is 30 days after that project launches. If that is the case, start dropping feelers out 90 days ahead of that milestone. Always be up front in conversations and interviews when you could be available (in a fuzzy manner). Work out a specific start date once an offer is on the table.