Research your destination(s):

• Travel Advisories. Read the relevant country travel advisories provided by government authorities. Choose an itinerary that takes into account country political, security and health risk.
• Visas. Make sure you known what VISA's are required for your trip and how long they take to acquire. Apply in good time so that you won't be disappointed. If you intend to work, special rules may apply.
• Health. The quality and availability of fresh drinking water. Check websites and seek medical advice to check which innocultations are required and how long before the trip they need to be administered - some innoculations require two or more injections. Make sure you understand whether diseases such as Malaria are prevalent.
• Medical. Ensure that you understand the rules about carrying prescribed medication with you. You may need to keep a copy of a prescription signed by your Doctor to show at border crossings and / or to authorities on demand.  
• Cultural. Understand the local social and religious culture to ensure that you don't make any gaffs that could get you into difficulty. These might include wearing in appropriate dress.
• Local Laws. Are there any local laws that apply? If you intend to drive you need o check whether your national driving licence is sufficient or do you need an international driving licence. It is vey important that you are well insured.
• Guidebook.  Purchase a guidebook for the areas that you intend to visit and learn about how best to 'get about', places to stay and to see. 
• Internet. Use the internet to investigate country and travel websites. Traveller blogs, maps, places to stay and to avoid. Check out your national embassy / High Commission website in the countryies you are planning to visit.
• Communications. Think about how you are going to keep in touch with those back home and how they can reach you in an emergency. If you are going to take a mobile phone:
  Do you need a Triband or Quadbane phone?
  Does your service provider have a roaming agreement in that country?
  How are you going to charge your phone?
  Should you take a tracking unit with a panic alarm or arrange for your mobile phone to be tracked in case of an emergency?
  If youintend to buy a local SIM Card, remember that you will need to let others have the contact number.
  Consider setting up a free interent email account if you don't already have one
  Make sure those at home have all the relevant contact details.
• Currency. Investigate currency that you need to take and the rules for exchanging local currency. Ensure that you understand how to get additional cash abroad whilst you are travelling. Consider travellers cheques.
• Border Crossings. Investigate border crossing procedures where appropriate. Make sure you understand what paperwork is required and the times of opening. You may have a long wait in some circumstances and / or some crossings may suddenly close. In some cases there may be a departure tax to pay.
• Weather forecasting. Especially important if you are planning to participate in adventure sporting activities, identify a relaible source of weather forecasts for the countries you are planning to visit.
• Other Issues. The list is not exhaustive. Learning as much as you can about your destination will help keep you safe and avoid disappointments during your trip.