The most important part of finding a new job is absolutely not to wait until your current job becomes unbearable. In fact, I subscribe to the idea that you should always be looking for jobs to a) know how your field is evolving and b) to stay apprise of your market value. This way when you do start to think about leaving your current job, you already have a sense of what's out there.
But still, you know what they say: looking for a job is a full time job. It doesn't have to be and I would know -- remember I just started a new job a month ago?
// 1. USE LINKEDIN ALERTS
Linkedin is a great first stop in your passive job search. The jobs feature allows you to set filters and schedule alerts for when jobs are posted fitting those filters. Depending on how active you want your search to be, you can receive emails daily, weekly, or even less frequently. Regardless, this app takes away all of the work of searching and delivers prospective jobs straight to your inbox.
// 2. IDENTIFY COMPANIES YOU WANT TO WORK FOR
Bearing in mind that you should never wait until you're miserable in your current role to start looking for a new job, identify companies that you would like to work for. This can be based on industry leaders, company values, word of mouth recommendations, or work culture. Many city based magazines will release an annual ranking of the best places to work -- start there. Once you've identified the places you want to work, keep an eye on their job boards or opportunities to network with their current staff. Networking with their staff may give you insight into their hiring process or staff goals like what jobs need to be created.
// 3. TALK TO YOUR (PERSONAL) NETWORK
Don't keep it a secret that you're open to new work! Send an email to your personal network alerting them you're curious about new job opportunities and what skills you bring and are looking to expand upon. People are far more likely to send you interesting job opportunities if they know you're receptive to the prospect of leaving your current role. Your personal network can also connect you to their professional network for informational interviews. You never know what will come from an informational interview; at worst, you have a 30 minute coffee with someone new and learn about your industry despite not leaving with a job prospect. At best, you get yourself in front of someone who is looking to hire someone like you now or down the road.
Most importantly when you're job searching, follow the advice of one of my mentors. She always said it's "this or something better". Don't leave your current job for another job unless you're certain it's better than what you already have.