First startup - Options Menu and controls

Ready? Start up Dota 2 and you will see an interface with a bunch of buttons. If you start the game for the first time, a message will pop up that asks you how familiar you are with Dota 2. If you are completely new to the genre, you should probably select "new". This way you will also meet other new players in the game once you decide to play versus other players, rising your chances to actually win the match. At first you will want to be comfortable with controls and adjust the game's options to your liking. I will walk you through that.  


Main menu screen:  

Enter the options on the top left corner.

you should set Audio and Video options to your preferences. The controls-tab will let you change the hotkeys you can use ingame. 
Here are some control basics, use them as reference later on, if you do not know how to control your hero. You should be fine by leaving everything at default for now and skip to the game options part. Note that you can access and change your hotkeys ingame as well, so if you want to find out which key you have to press for a certain function, you can always come back to this options menu.  


CONTROLS:



Left mouse button:
- selects units
- hold it to drag a selection box to select multiple units
- holding shift and left clicking units will add or substract them from your selection
- pressing "attack move" (A by default) and left clicking a unit order your units to attack the target; you can also use this on allied creeps below 50% health or towers below 10% health to "deny" them
- pressing attack move and clicking on the ground will make your selected units move to the point where you clicked and they will open fire as soon as they find an enemy unit on their way
- drag and drop items between your inventory, stash, courier and the ground (dragging an item from your inventory to the ground will make your hero drop it)
- ALT + left clicking will produce a ping that hopefully will draw the attention of your teammates to the pinged spot
- double clicking on a unit you control will select all units of the same type you control that are near your screen  
- activate skills and some items by clicking on their buttons
- open context menu when clicking player names in scoreboard, chat or friendslist


Right mouse button: 
- move to destination
- attack enemy if clicked on enemy unit
- follow allied unit if clicked on allied unit
- buy items in the shop
- open context menu for items you already own, allowing you to sell them, disassemble them into their parts (if possible) or drop them to the ground  


Dragging mouse pointer to the edge of the screen:
- move your view (camera acceleration and speed can be set in the game options)


Attack move:
- pressing attack move (A by default) and left clicking a unit order your units to attack the target; you can also use this on allied creeps below 50% health or towers below 10% health to "deny" them - pressing attack move and left clicking on the ground will make your selected units move to the point Move: - move + left click will make your hero move to the selected unit or place, this way you can also let your hero follow an enemy without attacking  


Stop:
- your hero will stop casting spells, moving or attacking. If you have auto attack activated, it will then immediately start to move and attack nearby enemy units


Hold Position:
- your hero will stop casting spells, moving or attacking. If you have auto attack activated, it will then immediately start to attack enemies in range, but stay at the same place


Control Groups:
- by pressing CTRL+the corresponding key to a control group, your current selection will be saved. The next time you press the control group's key, your saved selection will be restored. Clicking the key twice will center your view onto the selected units
HINT: summons from hero skills (like Lycanthropes wolves or Syllabears bear will maintain their control groups if they die and then you summon them again)


Control Group Tab:
- you can cycle through your selected units to use their skills by pressing that hotkeys. This will not remove your selection. Cycling goes from left to right and back to the beginning.  


SHIFT:
- hold it to queue move, attack and spell casting commands. your unit will execute them one after the other




self-explainatory, but important stuff:
Select Hero
Select Courier
Abilities (memorize those, it is very important that you use those keys to cast your hero's spell instead of clicking their buttons in the interface to be able to react fast enough)
Inventory (again, you will need to use those keys to be able to keep up with other players)
Camera (arrow keys to move your view)
Chat Team
Chat All  


not so important stuff, but might come in handy later on:
CTRL + ability key will make your hero learn the ability if you have a skill point available after a level up
ALT + ability key will toggle autocast on or off. Some spells are autocastable, most of the time those are attack modifiers like frost arrows, but also Morphling's Morph is an example for a autocastable spells. If you want those spells to activate everytime possible, then activate it, but be aware of the mana costs!
Select all other units: useful for heroes where you have to control units other than the hero 
Activate Glyph: reinforces your structures like towers and rax for a short amount of time (has 5 minutes cooldown)
Courier Deliver Items: the courier will deliver your items from stash to you and then go back to base Purchase Quickbuy: buy the item you've got in the quickbuy slot (see the explainations to the ingame HUD to find out what quickbuy is)
Purchase Sticky: will buy the stickied item, this is by default a Scroll of Town Portal Take Stash Items: will move items from your stash to your hero if you are near the fountain
holding CTRL+ left mouse button will enable you to draw on the minimap
Pause: if you need a short break, this key is your friend



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GAME OPTIONS:

Here are my preferences for starters:
auto attack: off (your hero will only attack when you tell him to or when he just killed a unit and there is another unit in range that he can attack) 
auto purchase items: off (you will want to have the control over what you buy always) 
auto select summoned units: depends on what you prefer, for starters on will probably be easier
double tap ability self cast: on (allows you to quickly cast some spells on yourself, that buff your hero or let you escape easier (for example Nature's Prophet's Sprout or Dark Seer's Surge))
unified unit orders: on (doesn't hurt to have) you can leave the other ones on default and set your camera speed and acceleration to your likings (I use maximum acceleration and 50% speed)


You can look through the other options and get an idea about what they do, but for now they should not be all that interesting to you. Don't get discouraged, you are about to be ready to start a game, even if I advise you to start playing alone or versus bots, because you clearly will need some time to get familiar with the game.