What to do depends on where you live, rural or city, as you'll see as we go along. These are in no particular order - just do them without a timetable. We go to Florida for three months every year and this is what we do.
MAIL - the post office will hold mail for up to 30 days. That's all mail. They have a form to fill out for this and you can either pick it up when you get back or have it all delivered on the date you pick.
If your trip will be longer than 30 days, they have a form to fill out to forward your first-class mail [and periodicals (30 days only)]. You should also plan to send them a form (same as the less than 30 days form) about two weeks before you will return. That way, they will forward your mail until the last two weeks and then hold it. The two weeks allows for any forwarded mail to reach you. Things like your IRS package will NOT be forwarded as it's not first class. Magazines and other periodicals can only be forwarded for 30 days so you'll have to notify the publishers of your temporary address. Otherwise, they're trashed. If you get to know your mail carrier well and give him/her a tip ($20 limit) and if they're nice and cooperative they MAY save second class and below for you. It will be unofficial so don't count on it.
THERMOSTAT - Depending on time of year and whether you're on air conditioning or heating, set the thermostat on 85(ac) or 50(heat). No sense paying for what you're not using. Leave the gas on, electricity on, fuel oil tank close to full. Arrange for automatic delivery.
WATER - If you have a well, unplug any water treatment systems (softener, etc). Turn off the circuit breaker(s) to the water pump and the water heater. Make sure these breakers do not control anything else. This will save a flood if your reserve tank, hot water heater or a pipe breaks. You'll have a small flood instead of a disaster. In the city, turn off the water at the main in the basement or wherever.
LIGHTS, ETC. - Make the house look lived-in. Get at least two timers (the ones with battery back-up) and set them in the family room and another room to turn on lights at dusk to 11:30 p.m. so the house looks occupied. The battery backup is so they stay in sequence if the electricity really is off for a few hours. Also get night lights (the ones that go on when it gets dark and off when it's light) and put them in hallways and bathrooms. Get a motion-detector exterior light. Unplug electronic equipment like computers, televisions, fans and items with remote controls, etc. Ceiling fans should be turned off at the wall switch. Electrical storms can trigger remote-controlled items. Some people have a small radio, tuned to a 24-hour station, on low, in an upstairs room so a burglar will hear voices and/or music.
POLICE/SHERIFF - Notify the police or sheriffs department that you'll be gone. They'll want to know if you'll have a vehicle in the driveway (make, color, license plate). Ask your neighbor if they would park in your driveway so the house looks occupied. Don't forget about your kids coming to town and using your house for a motel. Get their vehicles in the mix, too. The police do not need keys, but let them know who to notify in case there's a need.
KIDS - Tell your kids to turn on the water at the circuit breaker AND to turn it off when they leave.
SNOW OR LAWN CARE - Have a snow removal service (or a friendly neighbor) remove anything over three or four inches. Otherwise, let Mother Nature remove it. Make lawn care arrangements in warm weather.
EMERGENCY PERSON - Designate someone (neighbor or family member) to periodically (every two weeks or oftener) do a walk-around of the house (inside and outside) to ensure things are okay. Tell your two immediate neighbors who this is and how to get in touch with them. Make sure whoever you designate knows your cell phone number.
INDOOR PLANTS - Board out your plants to family or neighbors with care and watering instructions printed on 3x5 cards. Can't board them? Put them all on the kitchen table so the responsible person doesn't have to traipse thru the house to take care of them. Again, feeding and care instructions go with the plants, even to the kitchen table.
WINDOWS AND DOORS - Make sure all doors and windows are locked. Don't leave keys under rocks or mats or in the mailbox or in a flowerpot, etc. Give them to your Emergency Person.
NEWSPAPER - Take a vacation stop on your newspaper. This can be done on the telephone. If they need a restart date, add a week to your planned return date. You can always call them again to restart early.
BILLS - Arrange to have as many recurring bills as possible put on auto-pay. This would be electric, cable, telephone, credit cards, etc.
CABLE - See NEWSPAPER. Some cable companies have reduced rates while you're gone (maybe even zero).
CREDIT CARDS - Whichever credit card(s) you use for fuel or major purchases should be notified so you don't get turned down in some remote place because the card company thinks your card has been stolen.
FREEZER - Empty your freezer. All that food will spoil if the electricity goes out. And it'll really stink!
PEST CONTROL - Eliminate routine pest control while you're gone.
MEDICAL - Take your medicines with you. Make and/or cancel doctor and dentist appointments according to your schedule.
ANSWERING MACHINE - Set your answering machine with an innocuous message along this line: "Hi, we can't come to the phone right now. Thanks for calling."
LAST THING - Take the iron with you. That way you don't have worry whether you unplugged it.
YOUR TRIP - If you do these things, you'll be able to relax and have a good trip. Don't forget your checkbook and credit cards.