I'm so set in bringing two specific squaddies for each character that I even plan it ahead. It helps that my girlfriend does the same thing but picks different combinations. She's using Garrus and Tali on her first run.
For me...
Infiltrator - Tali and literal squaddie
Vanguard - Javik and Liara
Sentinel - Kaidan and James
Adept - Garrus and Ashley
Some of those I think will actually function really well as a team, particularly the Vanguard squad. When I do more Shepards I'll try a few different combinations as well.
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Gamertag/PSN-Murphiroth