Level 20 is great. I can move faster and fire a laser beam from my hands. Level 20 is great.
When I noticed I was less than 1 bar of XP from level 20 I decided to treat myself to a Warsong Gulch and after waiting a couple of minutes I entered and instantly won. I was actually pretty disappointed to win so quickly as it meant I was no longer level 19 and if I joined another game I would be the lowest level possible in that bracket. I quickly got over that fact when I realized I could now go and purchase my very own raptor mount and no longer have to walk everywhere. I still can't quite get used to level 20 mounts. Back in my day... never mind.
My leveling spec so far is purely shadow and I am focusing on anything that either increases my damage or makes me more mana efficient. When hitting level 20 I get the chance to obtain the Mind Flay spell which is one that all Shadow Priests love. It does some pretty decent damage and importantly it slows your target by 50%. This is great for any kind of solo activity and lets be honest, lasers are just fun.
Check back tomorrow for some of my best advice for leveling a shadow priest!