If it's not on Hardcore/Insanity, I'll usually tout around only non-biotics. (I really have a thing against Biotics), which usually leads me to Tali/Garrus badassery.
When on Hardcore/Insanity, I'll switch my party composition based on the prominent enemy type. I'm not going to bring Morden up against a group of synthetics, nor am I bringing Tali to shoot some organics, but I'll usually err on the side of Combat/Tech characters (Garrus, Kasumi) and one straight biotic (Samara).
I also tend to never bring Zaheed. I hate Zaheed.
For the record - this is with my "Canon" playthrough, which is always an Infiltrator.