Requirements

Make sure you have Steam version's of Arma 2, Arma 2: Operation Arrowhead and DayZ Mod.
Make sure you have Lingor Island v1.5 Map Installed. Found here.

AUTO ISSUE FIXER

Run this bat file it will try to automatically fix common issues.
Run as ADMINISTRATOR if not logged into an ADMINISTRATOR account.
Make sure you have no launch options enabled first for Arma2, Arma2OA or DayZ Mod.
 All of these Steam launch options should have nothing in them.
  STEAM LIBRARY->Arma2->Properties->Set Launch Options...
  STEAM LIBRARY->Arma 2 Operation Arrowhead->Properties->Set Launch Options...
  STEAM LIBRARY->Arma 2 DayZ Mod->Properties->Set Launch Options...
DOWNLOAD AUTO ISSUE FIXER


MANUAL ISSUE TROUBLESHOOTING

NOTE: Run STEAM as ADMINISTRATOR or be logged into an ADMINISTRATOR account.

FOLLOW THESE INSTRUCTIONS IN THIS ORDER
Verify Arma2 files, STEAM LIBRARY->Arma2->Properties->Local Files tab->Verify Integrity of Game Files.
Launch Arma2 to main menu then Exit.

Verify Arma2OA files, STEAM LIBRARY->Arma 2 Operation Arrowhead->Properties->Local Files tab->Verify Integrity of Game Files.
Launch Arma2OA to main menu then Exit.

Verify DayZ Mod files, STEAM LIBRARY->Arma 2 DayZ Mod->Properties->Local Files tab->Verify Integrity of Game Files.
Now you should be good to lauch DayZ Mod and play.

GETTING KICKED AFTER CONNECTING

Make sure you are launching the Steam version of Dayz Mod. NOT using DZlauncher or similar program.
Make sure you have no other mods enabled, STEAM LIBRARY->Arma 2 DayZ Mod->Properties->Set Launch Options...
Also check in game main menu -> Expansions. For enabled mods that shouldnt be enabled.
If still not connecting, Delete any locally cached mission files - C:\Users\{username}\AppData\Local\ArmA 2 OA\MPMissionsCache\*.pbo
NOTE: Show hidden files, folders and drives will need to be enabled from the windows folder options to see the AppData folder.

IF ALL ELSE FAILS REINSTALL

Uninstall Arma 2, Arma 2 Operation Arrowhead and DayZ Mod from Steam.
Make sure all files were removed from where they were installed.
Then follow the new Steam Arma install here.