Buy a one-way ticket. Have a rough plan for the first three months, including long stays, not moving every week. Where? Maybe it's time to get to know eastern Europe, Greece, and Turkey or head to Thailand, Malaysia, Indonesia, New Zealand, and Australia. Practice looking for lodging - hostels, WWOOF international, airbnb (great apartments and rooms within apartments) and other international rental websites, as well as 1-2 hotel websites, so you can devise a daily/monthly budget before you leave. No-frills budget airlines may be cheaper than trains.
There are expat blogs, State Department country profiles, travel blogs and Twitter accounts, and so many other sources of information to help you plan. Investigate and make decisions on whether to purchase international health or emergency evacuation insurance. Get a Visa Signature card (travel protection), but use a debit card at ATMs to withdraw cash - two of each recommended (one set to carry and one as backup). Make copies of your passport, drivers license, credit cards, prescriptions, and any other important medical information - one to carry in your backpack and one in your suitcase.
Pack very light. I took a small rolling suitcase and small backpack, light enough so I could manage easily on my own, including lifting up two steps onto buses and trains. Do not pack extra anything - replenish supplies as you go. Choose electronics carefully. With a Skype account and phone number, I traveled without a cell phone. I was very happy with the smaller MacAir, as I wanted a full keyboard, an external hard drive, a couple of iPods, a pocket camera, and a Nook for downloading library books. Do not take guidebooks.
As a solo traveler, I would talk to people everywhere - in transit, in markets, parks, restaurants. People loved to help with information and directions, to tell me what they thought about current events or the current state of the economy. If you stay in one place for 2-3 months, you can also check into what you might be able to do as a volunteer.
If you want to return to your current job when you return, ask for an indefinite, extended leave of absence. You may not be granted leave, but it never hurts to ask. Once you know your return date, you can start a new job search online, using Skype for interviews.