Here's a step-by-step guide through the process I used. You may find it helpful, you may not. This is a very personal decision to make and I'm not saying that this is the only way to think about it, but if you're struggling for a place to start here's my advice:
- Why are you unhappy?
I love lists, so the first thing I did was write up the pros and cons of my grad school life. If the cons are things that can be fixed (problems with coworkers, or if you like research but don't like your project), take a proactive approach and try to make things better for yourself. When I had "the talk" with my advisor they offered to let me change projects if that was the source of my unhappiness. It's dependent on the advisor, but if your pros list is longer than your cons you should probably sit down and have a chat with them. If the cons include things like "I hate working at the bench" or "research sucks" then I would move on to number 2.
- What was your goal in coming to grad school? Do a cost/benefit analysis.
If you're like me and you wanted to be a professor at a school that emphasizes teaching over research, consider whether that dream is worth your continued unhappiness for the next few years. I have friends that say it is, but for me it wasn't. Maybe you like labwork but you don't like the independent nature of PhD research? A Masters wouldn't be a bad way to go. You could work in a lab making more money than a BS, but with more guidance (and less freedom potentially) than a PhD.
- What do you enjoy doing and what kind of job do you want?
You still have to pay the bills, so what do you do now? This was an important question for me since I decided against both teaching and labwork. Do you like writing? Web design? Are you a salesman?
- Are there jobs available (where you want to work)?
It depends on your situation and the type of job you want. Some jobs are harder to find than others and might require you to move to where the opportunities are (ex. most policy jobs would need you to move to D.C.). If you have a significant other you aren't willing to move away from (my situation) then start looking at job listings in your area. Does anything look appealing? I started looking on Monster, and Indeed, and also searched for local job listing sites (many cities have these).
- Do you have a plan but you're still unsure about your decision?
Talk to mentors, family, friends. Lay out your reasons for leaving and your plan for after you leave. Sometimes it helps to hear someone else say "You know, it's clear you've thought through this careful and it sounds like you're making the best decision for yourself." Just be prepared, odds are not everyone will be supportive. (I actually returned to this step multiple times throughout the process.)
- The tricky part: Apply for jobs and then tell your advisor or tell your advisor first?
I struggled with this myself. I thought it would be nice to have a job all lined up before I talked to my advisor, but I worried that employers would be suspicious if I didn't supply my advisor as a reference. I was also worried that the more people I told the higher the chance that my advisor would hear I was leaving from someone that wasn't me. I finally decided to talk to my advisor first, which worked out quite well for me.
- The resolution.
Hopefully you should feel a rushing sense of relief that you've made the decision to leave (then you know it was the right decision for you). I can't tell you what happens next because I don't quite know myself. I tried to be as accommodating as possible to my advisor to ensure a good reference, which lets me benefit because I get to keep earning a paycheck while I continue my job search.