This page covers the events at the start of the game, during the initial Reaper invasion of Earth. This is essentially a prologue/tutorial section of the game, so create/import/edit your Shepard, and after some background chatter, the long-awaited but scarcely-prepared-for doom will arrive.
Once you’re finally in control you’ll be tasked with following Anderson, providing the game an excellent opportunity to teach you the basics of sprinting, jumping, climbing and vaulting over cover/obstacles. Eventually you’ll spot some Husks climbing a building ahead of you - pick them off, then climb down the nearby ladder, where you’ll be confronted with more Husks. Fortunately these critters are more enthralled by the nearby window than they are keen to kill literally the only person in the galaxy who can stop the Reapers, so take advantage of their shortsightedness and indulge in another tutorial: bash them all on the head with melee attacks.
When they’re dead, enter the building the Reaper kindly opened for you, loot a Medi-Kit (as a rule, these will either yield Medi-Gel or, if you’re already fully stocked, some XP) opposite the entrance, then open a door to continue. A Husk will rudely interrupt you, giving you the chance to practice a heavy melee attack. Once it’s been properly chastised, open the door and watch the scene that follows. Cryptic children are the worst.
After you regain control, pick up the Thermal Clips on the ground and reload your weapon. Follow Anderson until you get caught up in the aftermath of a dreadnought’s destruction, then pick your way across the rubble until you find yourself under fire by some Cannibals - advanced Husks capable of wielding weapons. Your cover is better than theirs, so you should have no trouble dispatching them.
Once they’re all dead, run across the platform, turn left, then continue forward and scan the Med-Kit on your right. Continue on until you find some more Cannibals in your path. Get in cover and pick them off, this time using powers, should you feel the need. Anderson has access to Concussive Shot, while Shepard’s starting powers will vary depending on what class you chose and whether you imported or not. For offensive powers, make sure the enemy you wish to highlight is targeted - you can aim while the powers wheel is up, during which time the game is paused.
Keep pushing forwards and pick up the M-8 Avenger Assault Rifle (which you’ll automatically equip) before accessing the radio. Now, when the Cannibals attack, you don’t have to fight them; the trigger for the ship to arrive is actually when you run out of ammo . So simply shoot your bullets into the ground from behind the cover on the far left and you’ll not run the risk of being killed (very useful on the higher difficulties). Once your ammo is gone, you’ll escape the planet to start your first mission.