When you are lucky: no need to hide the job search.
When should you hide a job search from your employer? Not when you are lucky and have a boss who supports you and your career development. She may be sad to lose you, but she will encourage you to make a move when there is no chance for promotion or salary increases in your office or in other parts of the organization. Your boss will enlist her network to help you make a change. Be thankful.
When you are not lucky: hide the job search.
When you work for any kind of Boss-From-Hell, loosely defined as someone who has created an atmosphere of panic and distrust, hide your job search. If you feel ill every time you walk in the office door and feel fine at the end of each day, hide your job search.
Do not ask for a recommendation from this boss. A vindictive boss will see your job search as evidence of disloyalty or more egregious failings. She will fire you the minute she learns that you are looking. Hide your search. Keep your secret safe.
Always read and heed advice from Amanda Ellis. A blog post for everyone to read. Pronto.