The spec you play also slightly depends on your playstyle... this is the spec I play right now:

http://www.wowhead.com/talent#jcd0bZGcRrfzRdbu

a variation of it:

http://www.wowhead.com/talent#jcd0bZGcorfzRdbub


I did not start off using these specs however, the following spec spec is also much easier to play and helped me get used to dks in the arena especially when you are not used to timing strangulates.

http://www.wowhead.com/talent#j0oZGcRrfzRdbufM