You should also make sure that it's topped up with fuel as this will help prevent corrosion in the tank. It's the same for anti-freeze. Lubricate and grease any nipples and make sure the car is clean and polished if you have time. Don't use the handbrake. You don't mention what age of car you have, but a trickle charger is essential with a modern classic at a flat battery causes multiple problems. We'd suggest only starting the car if you can take it out for a short drive as well - if you can't, consider removing the spark plugs and turning the engine over by hand (if you're uncomfortable with this or unsure how to, then don't try it). If the area you're storing the car in is damp, consider a dehumidifier. Finally, don't cancel the insurance as you'll still need the car to be covered for fire and theft.