There's basically a few tips you need to know if you want to survive a decent amount of time.
First, here's the map of Chernarus:
http://i53.photobucket.com/albums/g64/PoorOldSpike/Competitons/AA-inlet1.gifSecond, avoid Chernagorsk entirely. Only enter Elektro if you are almost going to die from hunger or thirst and ARE ARMED. In all likely hood you will never make it out.
Third, if you are able, kill everyone. There is absolutely no incentive to team up right now and chances are your teammate will get you killed.
Fourth, whenever you can see a zombie, you should be prone. That means laying on the ground. Never stand up ever unless you are being chased by zombies. If you are being chased, run to a dense area of houses and confuse them by running through tight spaces. When you are sufficiently far away, jump to the ground by pressing Z and move away. Use crouch walk (x) when moving between towns)
Fifth, never use the Lee Enfield or unsilenced sniper rifle in a city. Ever.
Sixth, if your blood is gradually decreasing, bandage immediately. If you have no bandages, look for them. You do not regain blood and the only way to force yourself to is to eat food which is difficult to acquire or get a blood transfusion which is even harder.
And finally, always play in the dark and try and immerse yourself otherwise the game is boring as forget.
