Preparing for a trip
Those that who ever done a major trip overseas will know that even the most spontaneous of trips requires a degree of preparation. Without some consideration before going on your first trip overseas you could be caught short. It does also pay to have some kind of itinerary and a guide book of some accommodation that you might need when getting there.
Some people go much further, and it is always recommended to get some accommodation for your first week overseas. Definitely if you are going to be arriving in the most busiest season. Bear in mind that in the southern hemisphere that Christmas also happens to be in the height of summer. Events occurring locally such as sporting events can make accommodation harder to find and in some cases more expensive.
Check the following:
If you have a passport check long in advance that it is going to be valid for your trip. Some countries require you to have 6 months of validity beyond your trip. If you think this going to be a problem renew your passport earlier. It is far more easier and often cheaper to get your passport renewed in your home country then using an overseas embassy, consulate or high commission.
Next next if you are going to need a visa. Some countries don't require visas, some just a travel authorization such as the US or Australia, some require visas long in advance. One such country that is not the one for spontaneous travel at this time is Russia. Many other countries require visas but this all depends on your nationality and where you are coming from. It can also depend on your intended length of stay too. If you have previous convictions you may also need a visa, so check with the country's embassy or consulate long before you intend to travel.
Decide what you are going to need
You don't necessarily need a major list but make sure you have the essential items that you need for your trip and that you are not taking too much for your airline. Considerations might include, the climate and indeed what clothes you wish to take. But also yourself, whether you wear contact lenses, whether you suffer from a condition such as asthma and any other needs you might have. If you are going to drive overseas do some research and check whether you need an International Drivers Permit.
Take a Snack for your trip to the airport
Unless you live within walking distance of the nearest international airport, you are going to have to plan that trip too. Take a healthy snack with you, as it could be the last thing you eat on land for a while. It will help you get through your trip and all that waiting to get boarded onto your plane (or ship!).