You may not get much warning so pay attention to the news. There could be a minor item about new deaths from a known disease in a foreign county. Then possibly another news item about the disease causing even more deaths - this time North America. At this point you need be be paying close attention - is the disease spreading rapidly? How close have the deaths been, etc.? If 1 death one week, turns into 6 deaths another, then 36 a week later and it's getting closer to you - it is time to start considering bugging-out. It is likely that by the time you hear the word "pandemic" used in the news - it will be too late.
As you are watching the news, remember that government agencies have a vested interest in keeping people calm. If people are panicing, stores become overrun as people stock up, there may be runs of banks, markets could crash, etc. All of which adds more work for government bureaucrats trying to maintain control, and hurts public opinion of elected officials which messes with their politic career. So just keep in mind that things are usually worse than the government would let on.
Avoiding other people will be important to surviving a global pandemic. During the Plague of the middle-ages, those who were most likely to survive were those who could afford to stay isolated.[*] So you want to bugout to some place very remote, and stay there.
Should you decide to admit a family member or friend to your bugout location, keep them isolated until the incubation period is over. Food, water and first aid supplies should be given such that the person remains isolated.
If the pandemic is spread by birds - like an Avian flu - you will need to be extra-vigilant in purifying water, and sanititaion.
Remain positive - barring a nuclear war breaking out too due to world instability, a global pandemic would be resolved after a few years. Some people would be resistant which could form the basis of immuninization. Also, medical science has made huge strides from DNA splicing. Today, some cancers can be cured by splicing cancer DNA with human T-Cell DNA - creating T-Cells that attack the cancer.