My first time through I played Paragon as described by Mollusk. Took the Renegade actions I thought were too good to pass up.

Namely, not letting that Batarian bastard get away on the Asteroid. The way it was framed back when I did it the first time, I thought that by letting him go, he was going to undo my work on slowing the asteroid. Guy targeted 4.4 million humans. No, no. Dying in your sick bed by the third game is far too good for you, Batarian.

My next time through the entire trilogy I tried in vain to max both Paragon and Renegade. I got them both high enough that the only thing I got locked out of by the end was making Illusive shoot himself.

Actually choosing way more Renegade options was really refreshing, and some of them were actually quite surprisingly for the better in all aspects. Better end results, better short term and long term etc.

The scars on my face flip flopping was also kinda funny too. One mission they're searing orange, cracking my face apart. By the middle of the next mission they're mostly healed again...

Also I romanced Liara and only Liara the whole of the second playthrough. I thought it'd make the final mind meld she does for farewell better in ME3. But I actually wound up preferring that scene without the kissing. It's a little more romantic without the kissing, honestly.