Most of us move from one employer to another at some time or other, some do it more often than others. As just one example, I worked at a number of jobs before we started Eagle.
It is never a good idea to leave on bad terms, because its amazing how small the world becomes in time.
Some hints for leaving with your head high:
Put yourself in your employers shoes. What would you like?
If your contract of employment calls for two weeks notice ... give two weeks notice, at least.
Be up front and honest about where you are going.
Be as honest as you can about why, but do it in a positive way. Don't burn people on your way out!
Don't knock your old employer.
Don't play up your new job to those left behind. Your decision to leave is yours, creating a "buzz" about leaving can cause ripples.
If working your notice period, work even more diligently than your normal operating mode. Despite what you think, it will be noticed and appreciated.
Be grateful for the positive aspects of your old job, at the very least it helped pay the bills. Probably you learned some stuff, and added to your life experience.
When you are gone only have good things to say about the old company.
If they call looking for help be professional and as helpful as you can.
If you have contractual obligations to your old employer ... honor them!
Leaving on a sour note will "bite you" at some point! Being courteous and professional will cement a positive reputation ... but more importantly it's the right thing to do! PS. If you are an employer then you also need to do the right things when an employee leaves.