How to be good at supports.

Introduction

Hello, my nickname is morningduck and i am 5.3k mmr support player and the reason that i play supports is my mindset. I think that if i'm better than my cores i should support them, so it will be easier for them to play. Kinda cocky, but so far it works.
What it takes to be a good support? How to move around the map to be impactful? How to help your cores win the game? How to be useful in mid and late game, if you have no little or no items? Hopefully, this guide will help you answer these and many more questions.
This guide contains 4 parts:

1. How to be a support.
2. How to be good at positon 5.
3. How to be good at position 4.
4. Warding.

Let's begin!

Part 1. How to be a support.

Most of the people tend to think, that cores win games, but i'm here to tell, that supports do as much or even more work than carry or mid. Playing support you should be aware of everything that happens on map yet don't miss a thing under your nose. As a support you'll often pick your hero first. It means that enemy team will try to counter pick your hero. The thing is, there's supports that are solid versus almost every hero in the game such as Lich, Spirit Breaker, Earthshaker, Jakiro, etc. The most easiest way to find heroes like these is to go to Dotabuff/Opendota and see what heroes have the most winrate this patch.
If you feel very comfortable on particular hero, you can pick it any time you want, but keep in mind, that if you pick hero like Io you can be countered by very popular Lich and not very popular Ancient Apparition.
As important it might be to pick good hero first, you'll need to know how to counter pick of your enemies. If you're not sure what to pick, the best way to decide is to go to Dotabuff, search for particular hero/heroes and then decide who to pick.
Note: consider trying to ban heroes that might counter your hero, even if you really don't want to play versus Bloodseeker. The most important thing to do as a support at laning stage is to take every bag of gold and every chunk of experience that you can take without hurting lane of your carry. That means that you should do pulls, take bounty runes, gank and take free lanes.
It's very important that you help your lanes, because in this patch it is critical to secure your early game, especially when you play a pub game. Spend your resources and time where you can make a difference, use smokes, don't hesistate to help your mid: it's good if you help your mid hero secure 2-3 spawns of creeps at the beginning, it's also good to assist him if enemy support babysitting mid (if you can't, then try to kill/give nothing to enemy on other lanes).
I should mention, that every your death matters, don't think that you can die as support and there will be no consequences. Insteaad, you should really focus on not dying, but if you need to die, for example, to kill a enemy mid or win an early fight, then it's worth it.
Also,don't forget to use your abilities, that give you advantage on lane, such as Sacrifice, Demonic Conversion, etc.
In conclusion, I want to say, that the most important stage for most of supports is laning stage, because your influence on the whole game comes from it. Entering the mid game your influence on the game weakens, because by the time of midgame cores have at least one good item (such as Armlet of Mordiggian, Blink Dagger, Sange and Yasha etc.). And from now on your impact in fights becomes less and often determined by use of your ultimate ability or your major spell (major spell is the most important spell of your hero, for example, Meat Hook).
In the late game you probably will have some money, so items like Glimmer Cape, Lotus Orb, Force Staff, Pipe of Insight and so on, will be your cores' best friends. And from now on your focus should be on your and enemy's main carry(s). Also remember, that buying right item, even on support, can turn the game into your favor. Supprorts are very important aspect of the game as any other role. Don't think that's very easy to play support, nothing is easy in DOTA 2. Be efficient, be aware of the map, be useful, be smart.

Part 2. How to be a good position 5.

Position 5 support is usually the guy, who buys all the wards, have only glimmer cape + brown boots at 30 minute mark, not afraid to save your core or secure him a kill even if it's means that you'll die. Dudes who inspired me to play position 5 like this are Solo and PPD. There's not really much to write about except don't pick something greedy. Supports like Ogre Magi , Winter Wyvern (yes, it is a good hero in a lot of situations, she sucked only at the Main Event of TI, in groups she had very good winrate), Dazzle, Disruptor are usually good at positon 5. Your goal as a position 5 is to buy cour, wards, upgrade courier, and the most important is to secure good lane for your carry/mid. Don't forget to stack your jungle, it is critical to stack ancients if your team has Sven, Bristleback, Templar Assassin. Use early smokes to gank mid and place wards. Have a tp to save your heroes and maybe get some kills for your team. There's not really much to say about this topic, because i said almost everything you need to know about it in first part, but there's still some information left to say.
First of all, it's a lot harder to do impact in fight as a position 5 compared to position 4.
Second of all, in most of situations you shouldn't pursue items, that have expensive parts (like Scythe of Vise). Only buy these items, if your team really need it/game went really late/you can afford like 2/3 of it at once. Presumably you'll have only items like glimmer cape and force staff if you play ascetic type of position 5, which sometimes called position 6. But, you still do a lot of impact on the game, though it's a lot harded to do.

Part 3. How to be a good position 4.

Position 4 is often a roamer, but in general it's just support who takes farm over other support and buys less support items. I'll talk only about position 4 as a roamer position, because i am not really sure what to say about position 4 in trilane, for example. When you pick position 4 support, things are a little bit different. You need to adjust based on enemy's picks and possibly take heroes that make a lot of impact. Your target as a roamer is to kill enemy heroes. Simple? Not really.
There were some games that I did a huge mistake: i tried to kill at lanes, where heroes were too strong for me and my teammate to kill. So i threw my early game by this move. Try not to do this, learn to evaluate your strength.
You should collect bounty runes, often enemy offlaner won't take his rune so it's basically your rune. Go and take it. Easy gold.
Also, don't think that because you're position 4 you don't have to buy wards. Sometimes you need to help a bit with support items.
Your succes in mid and late game directly linked to your early game rotations. On a lot of position 4 heroes you'll have your core items in mid game ( Blink Dagger on Earthshaker for example) and this is the time when you can truly shine. Jumped into 4 people with Echo Slam - won a teamfight which can lead to winning the whole game for you.
It is crucial to use your farm efficiently, so you can impact the game the strongest way you can.
Also, in the late game you'll have more space to farm, if you're not losing, of course. And with farm you can become core on certain heroes ( Nyx Assassin , Night Stalker and some other) Evaluate your strength, seek every piece of farm you can and use it effeciently and don't forget to help a little with support items.

Part 4. Warding.

It will be a really short part, because there's too much to say about warding, so i'll just briefly explain some basics.

Wards are the things that you place on the map. They can win you the game, if you know how to ward, or be useless, if you don't know how to place them. One of the most important items in the game costs 60 gold, but their gold/efficiency ration is the best among other items. There's two typer of observer wards: agressive and defensive.
Agressive wards are the ones, that you place, for example, in the enemy jungle, when you're losing. Basically, you should place agressive wards, if you know that you can pick off enemy core, which would laed to destroying objectives or make it easier for comeback in the game for your team.
Defensive Wards are the ones, that you place, for example, in your jungle. You should place them when you need to avoid ganks, hold control of your jungle, enemies farm in your jungle.
I think, that in most of sutuations you need to keep balance between these two types of wards, although there's no point in defensive wards, when you have all the lanes and enemy has no lanes. Place them to deward, to defend yourself at laning stage versus invisible heroes, and when you're going to push versus heroes with invisibility, when you're doing roshan. First of all, I encourage you to go and read guides about warding, because you won't be good at warding after reading this part, but I felt that it was really important subject, so i decided to write about it at least something.
Second of all, buy wards.
Third of all, please leave links to guides about warding in comments, so i can include them here.

The end.

This is THE END of my guide, hope you found it useful. If you feel that my guide lacks something, please post it in comments, so i can include it. Also, point out my errors and send feedback, thanks.