1. Ask ahead of time what the company will and won't pay for, and how expenses will be covered. For instance, some employers will pay for a plane ticket and hotel room, but won't cover meals or transportation while you're in town, while others will pick up the bill for everything. You also want to know whether they'll pay some bills directly, or whether you'll be expected to pay up-front and get reimbursed later.
2. Try to arrive early if you can. If you have to race from the airport straight to your interview, you risk arriving flustered and on-edge. Try to arrive early so that you may take your time and not feel rushed. In fact, if you can arrive the night before, that's often easiest.
3. Keep any other plans for the trip flexible. If the employer is paying for your travel costs, you should be available when they want you to be. That means that if you make plans to see a friend who lives there for dinner and at the last minute the company invites you to dinner, you should cancel with your friend so you can accept the invitation. (Obviously, let your friend know in advance that this might happen.)
4. Bring two sets of interview clothes. Even if your interview is only scheduled for one day, there's always a chance you'll be asked to come back the next day to talk further or to meet with additional people. If you are, you'll be glad you have another set of professional clothes to wear.
5. Be frugal in your expenses. If the employer is paying for the trip, don't spend their money extravagantly. Fly coach, choose a mid-range hotel, don't splurge on fancy meals, and don't rack up room service and pay-per-view charges. Assume that the employer may review your expenses with an eye toward whether you were financially responsible for their resources or not.
6. Be in interview mode the whole time you're in town. It's entirely possible that the employer will hear about it you're rude to the hotel staff or to the person they sent to pick you up from the airport, or if you drank too much and fell asleep in the hotel bar. Be on your best behavior the whole time you're in town.
7. Explore the area. If you're considering taking a job in this area, it's important to make sure not only that the job is right for you, but that the area is too. If you have time to explore, don't just hit the tourist destinations; try to get a feel for the neighborhoods, walk around downtown, hang out in a central location and people watch, and do other activities that will help you envision what it would be like to live there.
Alison Green writes the popular Ask a Manager blog, where she dispenses advice on career, job search, and management issues. She's also the co-author of Managing to Change the World: The Nonprofit Manager's Guide to Getting Results, and former chief of staff of a successful nonprofit organization, where she oversaw day-to-day staff management, hiring, firing, and employee development.