
Remember to pick up a weapon specialization or the Widow rifle. Mordin and Miranda for a main story mission. I usually do Miranda's loyalty at this stage.
One random mission so the game unlocks the next one. Nothing story- or gameplay-wise. Bring who you like. Miranda and Garrus for dual Overload against Geth shields. Bring Miranda when you can, but Liara is your best squadmate here with her Singularity. This is often done later in the game, but: (1) if Liara was the ME1 love interest, Shep should go see her as soon as possible (2) even if not, the Shadow Broker ship becomes a hub and source of upgrades, as well as the ability to retrain squad powers. Important story-wise to have your leads, and Warp and Incendiary are useful against Scions and the Praetorian. Garrus and Miranda for dual Overload against many shields. Mordin and Miranda for best powers Mordin and Zaeed for best story (but too bad that Zaeed only has one line in a mission full of Blue Suns mercs.) Plus a cool Prothean sphere in Shep's cabin. Firewalker. Irrelevant story-wise, but 625 XP, 30k creds, and 10% biotic upgrade.
Also check out the party dialogue for some hints on future missions. XP, 60k creds, tech upgrade, unlocks Flashbang Grenade, and you find the Locust, the best SMG in the game. Mordin will be useful story-wise and is a great squad member too.
Go to Omega right away as suggested by Illusive Man.
On Omega: one dialogue to unlock Zaeed in squad. On the citadel: one dialogue to unlock Kasumi in squad. See Anderson, get reinstated (or not), do some side assignments for quick leveling. First thing the new Shepard would do is visit her old ship and collect the dog tags.
Cerberus station, Freedom's Progress, Normandy.