WHAT TO BRING
If you are coming from overseas, there are a few special considerations you should keep in mind. Even if you are coming from a country that speaks Spanish (or you speak Spanish), there will be a multitude of changes for you to assimilate in the beginning, and anything you can do to lessen that will help you adapt more quickly.
It is highly recommendable that you first visit the area you plan to move to, and try to get your bearings (where are the places you will need to go from there located? i.e., school, supermarket, workplace, gas station or other means of transport). A good idea, when moving abroad, is to rent someplace for a while (unless perhaps you already own), until you can decide whether you want to stay in the same place, or perhaps somewhere else that would be more convenient. You may not know where you are going to be working, or where your children will be going to school, though of course these are things to keep in mind when you are deciding to move.
Also, when you leave your current location, it might be wise to stay on after all your things have been shipped, as you will undoubtedly need time to tie up loose ends. Otherwise, you might need to return briefly, one or two weeks after the move.
If you have chosen to move, but are not being sent by a company, one obstacle you may encounter is the cost of moving all your belongings. Depending upon what you have and how long-term or permanent your move is to be, you may want to consider either leaving the bulk of your belongings behind in storage (with that cost to factor in), or selling some or all of them.
The less things you have to move, the easier it will be, though of course once you get to your destination you will need to get at least some basics. People who move often are amazingly good at keeping things to a minimum, and usually rent furnished lodging until decided about the permanency of the move.
You can pack some suitcases with your more personal belongings and send the rest, either by mail (if it's not too much), or with a moving or transport company. Do be sure to insure your belongings (often the company will include this in their price), and of course make certain you take any important papers or valuable things such as jewellery on your person. If you are moving with pets, they will need a veterinary certification of health, and proof of proper vaccinations (contact the Spanish embassy or consulate in your area for up-to-date requirements and procedures). And if you are coming by plane or other public transport, there may be fees and restrictions for pets, so become informed ahead of time. And don't forget to have all the necessary passports, visas, vaccinations, and tickets for everyone!