Personally I use the launchers provided at the dayz website than the steam version due to the fact it makes server and map browsing much easier and faster. Keep in mind dayz is much more fun when you have a friend to help you, so if one of your friends has dayz installed play with them! Keep in mind you will likely die a lot in the beginning so just keep calm and keep going.

Ideally for a new player you will want to find a server with 20 or less players so you don't get killed before you can actually experience the game. Once you have found a server keep in mind if you log out your belongings will remain in your inventory. Congratulations you've completed the hardest part of playing this game, finding a good server!

You have now spawned in somewhere along the coast of chernarus. If you look at the bottom left corner of your screen it should tell you where you are, this is important as over time you build an understanding of where places are in chernarus. The controls are pretty basic and you likely already know them so the only thing about them im going to go over is the inventory controls, open your inventory with G and to use items like bandages right click them and then click the option you want.
Now, you need to see what you have as different servers have different starting gear. Generally you will spawn with some sort of pistol usually a revolver, M1911, or makarov. If you spawn with a makarov you should replace it as quick as you can as it has really low stopping power. You also may spawn with a map which is very useful (you can place private beacons that will appear even after you put the map down by shift-clicking on the map).
Look around and observe your surroundings find buildings and see if you can enter them. Be sure to avoid cities at first as while loot is common there they are also filled with players who can be very hostile. Collect your loot and move to a safe place to plan what your next move is.

You ideally want a pistol with two mags or more, at least two to three bandages, some food and drink, and a main weapon with two or more mags. Things that are also helpful: water bottles (they're refillable), knife, map, hatchet, and flashlight. If you can't find a weapon you can use a hatchet, machete, or crowbar as a melee weapon that will take up your main weapon slot, while these weapons have short range the have really high damage and are silent.
If you found a main weapon on the coast it is likely a Lee-enfield(high damage but loud), a double barrel shotgun(low capacity but can use slugs or buckshot like any other shotgun), or a Remington 870 pump action(high capacity plus a built in flashlight). I recommend using your pistol to kill zombies as they are quieter and ammo is more common, and your main weapon for players and emergencies as they may be loud but they have greater stopping power.
Your next move should be to head north specifically to stary sobor or any northern airfield as there is a lot of military equipment in those locations(including vehicles). It's a long walk and there are many dangers but moving through the woods negates many. You likely have helicopters pass over you some may be only npcs but others can be players with hostile intent. Going prone makes it incredibly hard for a moving helicopter to see you and being in a forest almost gaurantees safety from the air. The next few sections will describe the other dangers and most importantly nightfall which is a big game changer.

You have survived this far and probally know how to deal with zombies but the real danger is players. Friendly interaction with players is very helpful but is the most risky thing in the game. A call for help on the chat may be an actual person in need of distress but can often be a trap set by clever bandits.
Have a comfort zone if a player gets too close the best bet may be to open fire, but make sure to voice that you don't want them any closer so you don't end up killing someone who had pure intentions. Bandits come in many catergories: loners or groups that would normally not kill you but are forced to by nessacity or you got too close for comfort, people who are untrusting often from interaction with other bandits, people who actively hunt players down for loot, people who bait others to their doom, and scavengers who don't trust you or want you knowing where they are or taking loot from the area.
Stealth is your friend! Evasion is the most sure fire way to survive, is that loot in town worth messing with the heavily armed man going in? Avoiding contact with fresh spawns can be important too, they have no loot to lose and only stand to gain by killing you. It is wise to avoid announcing your position in side chat as those who you don't to see it will. Scout an area first, identify possible threats and remove/evade as needed. If you rush in even non-bandits will probably try to kill you.

Well you've lived this far so you know what this could mean. Nightime makes it very hard for zombies to see you but in turn it becomes VERY dark (darker than it is in many games). This means scavenging becomes easier you can move without as much threat of being seen but seeing becomes very hard.
there are several ways to see clearly at night from most common to rarest they are: chemlights(small area of light useful for lighting interiors and keeping track of teammates), flares(intensely bright wide are of light great for outdoor illumination but very visible from a distance)
Flashlight(illuminates circle in black and white less visible than other lights but requires you to put in your secondary slot, mounted flashlights excluded) Military flashlight(illuminates wider area in red which creates nice contrast if something moves, like a player) Night vision(undetectable by others, limits view illuminates the best out of all solutions).
Be wary this does not make you safe as bandits know many are out to scavenge and sometimes actually go to large towns and kill survivors as they come to loot.

Congratulations you managed to read through all of this and may put it to good use. You will be able to learn the rest yourself and will hopefully go on to try other maps and maybe mods for dayz, i personally recommend either breaking point mod or the overwatch mod and the overwatch mod is available on the dayz commander launcher which i also highly recommend. I hope i have jumpstarted your gameplay from new guy to veteran at least a little bit quicker and if requested i may make a guide for some maps or mods. Have fun and dont let the bandits sneak up on you!