How can I play Dota 2 Beta?

I know DotA 2 is still in its beta phase, but I see more and more streams from DotA 2 players. And I would like to play too, rather than only watching!

How can I get a DotA 2 Beta key?

Donation Method - Ask a bot for a Spare Key!

There is a Steam Community bot that people donate extra DotA 2 keys to. You can add the bot as a friend and send him the private message "give dota" to get a DotA 2 key sent to you. You can donate any extra keys you end up with afterwards.

New Method - Buy the access to Dota 2 Beta

Valve gives now the possibility to buy directly an early access bundle through Dota 2 Store. The bundle contains the beta access key and some collectibles.

Old method - Join contests/giveaways

Beta Giveaway Contests (by Dota 2 communities)

One legal and legit way, is to participate to one of many contests available and hope to win. The official community of Dota 2 is PlayDota. I suggest you to register to to that site, because since the launch of Dota 2 Beta it was the main beta key distributor, through random beta keys giveaway (hundreds if not thousands key already distributed).

There are many other places around to check and it has no much sense list all sites here. Just check PlayDota forum and Dota 2 Reddit Channel, that are the two main Dota 2 international community sites at the moment. If a new giveway starts, it is usually advertised there.

SteamGifts is also an interesting community driven gift website (that support Steam logon) that often has Dota 2 keys.

Beta Tester Selection (by Valve)

If you don't have time, skill or attitude for a contest, you can try to install Steam and fill this survey.

It is an hardware survey followed by a simple questionnaire that will be used by Valve to target potential beta testers. Identified subjects will receive the beta access and 2 additional keys to invite some friends.

Other sources

Be aware of scammers sites or people that try to sell you fake keys, there are many around. Also buying valid keys infringe Steam rules, so just avoid it.

A lot of Dota 2 keys were given away in the recent Christmas event. They are stored in people's Steam inventories, which are tradable. Dota 2 key are very valuable though - I've seen some trade as high as a copy of Skyrim or MW3 (though most go for a bit less).

So, find someone who wants to trade away their Dota 2 key, and get to trading!
Some good places to look are TF2outpost.com, SteamTrades.com, SteamExchange.com, and the Steam Trading forums. If you have the game the person offering Dota 2 is looking for, or you are willing to spend a bit of money to get it (keep in mind you can now trade for coupons to make some games cheaper), you can easily find a Dota 2 beta key.

Happy hunting!

Try this website: Dota 2 Championships

There is a link that is almost on the bottom of the page that you can sign up for the beta through your Steam account.

Also, it would seem that Play-Dota is giving out codes: Dota 2 Beta Key Draw

You can also buy a beta key on the Steam Market thingy.