How do I tell my boss I'm unhappy?

timing should be the key. you cannot tell your boss such thing when he/she praises you for the good work (if ever!). but if he/she drops a hint about the hard times the firm is going through, now grab the moment! dont make it sound like you expect pity, state things in a clear concise manner. then wait...

Maybe politely explain to your boss you are not happy, and wonder if you both could work together to find a solution that keeps you both happy.

Just calmly email, or talk to him about the reasons you are unhappy. Suggest some solutions also to help with this issue. Remember to not be angry or too confrontational

This is a tough question because bosses may or may not be understanding. I would write out a list of what I"m unhappy about. Then I would prioritize the list to what are the most important issues if more than one. When approaching my boss, I would seek a private location such as an office where others won't hear the conversation. Be as polite as possible, but maybe try being honest and assertive in your discussion. Try not to get upset if the response isn't positive. Perhaps consider giving some ideas on what could make you happy such as more hours, more responsibility, etc. As easy as it would be to let him mind read my thoughts, remember bosses are not mind readers, and they need you to clearly and reasonably present your concerns and unhappiness.

Tell them outright. Its often much better to just blurt something out. You'll feel better for it, like a weight has been lifted from your shoulders, and if they are a good boss, they will understand and ask you what support you would like from them. If they don't do then they're not worthwhile, to put it bluntly.

I think about why I am being unhappy and how it is related to my work. I also think about what I expect from my boss and how he/she can help me. One I am clear on those I ask for time to meet with him/her to discuss some personal topic and I explain the situation I am being, how I am feeling and what do I expect to see if we can find a middle ground and agree on a solution together. What I expect might not be the same he/she can offer, but it is important to look for some compromise together, so you can start feeling better and your boss can provide you the support you need.