The usual precautions are always advised.
It is better to travel in a group than alone. Have photocopies of your passport, tickets and credit cards in case the originals are lost.
Know the customs and conventions of your hosts. See your GP before departing as vaccinations may be recommended by some. The tap water is clean and safe in Vanuatu. Always eat and drink safely and wear clothing to decrease chances of being bitten by insects. Take plenty of appropriate sunscreen lotion.
You must see your doctor for shots and medications before you travel to Vanuatu. Among other things, malaria and hepatitis A are both present in the area. You will need to take anti-malaria medications before, during, and after your trip, and make sure that your vaccinations are up to date.
You should also make sure that you pack a first-aid kit to take care of any cuts or bites you might get. Small cuts can get infected very easily in tropical climates.
By taking precautions, you can ensure that your trip to Vanuatu is both safe and fun.