I'm in the process of playing through the ME series. I was an Infiltrator in ME1 but wanted to mess with Biotics in ME2. Initially I was a Vanguard but I wasn't a fan so I switched to the Adept and was just wondering if there's a general rule of thumb to playing one.

Use biotic combos and make sure you micromanage your squad. The Adept is a glass canon, so you need to stand back and let your squad do the shooting while you hit enemies with spells, especially key on insanity level.

Its been many years since I played but I would enter a combat area, spot the enemy choke points, and arrange both my squadmates either to the left or right, not both. The AI focuses on Sheppard so you can draw their fire and have the squad flank. For most of the game I play with at least one other biotic on my team sometimes two, you can set off devastating combos firing a warp into a singularity, or pulling/throwing enemies into a singularity.

I found this youtube series particularly helpful when I played on hard.

http://www.youtube.com/playlist?list=PL555DF95B6D6BF40C