I'm starting a new D&D campaign. I'm still fairly new to D&D and I want to build a Rogue/Assassin that dips into Swordsage for the assassin stance. I have read on other sources that this is the best option. I want my character to be high damage output and always be behind the enemy. My DM has given me access to all 3.5 material to play with. How would I go about building this character?