Very important. A group is the way to be able to have people assist you, have medical care, and to be able to survive more easily. But be careful with who you chose to be in the group, or what group to join in too.
Common sense is the way to surviving! Make sure to check everywhere before you stay at an area. Thinking about going alone to piss? Think again. Trying to be a hero in a dangerous situation dont be, im not saying you shouldnt, but be careful when you do.
NOTE: Avoid Populated Areas, sorry for the mistake. Avoid populated areas such as movie theaters, huge markets, basically any large buildings. In which you can find many zombies which you will become eaten for a non smart move.
A sidearn is a quick weapon to pull out in just the amount of time to save your life or go another way. A good sidearm could include a pocket knife, pistol, etc.