Important Note: This walkthrough was written for the 'Hard' difficulty. It is in any case recommended that you play the game on Hard yourfirst time through, or it may very well be much too easy.
Only if you're an inexperienced gamer and have difficulties with the controls should you play on Normal (or Easy). The most notable difference between difficulties is the amount of items you'll find during your journey.
The easier the difficulty, the fewer items you'll find. It's thus quite likely you'll find items not listed in (the current version of) this guide when you're playing on Normal or Easy, although you'll still find everything else just fine (which should be more than enough).
After the scene you'll get out bed as Sarah. You can inspect the phone one more time, but it doesn't do much good. It's also possible to check out the birthday card on the desk. After this, head through the door and search the bathroom to read a newspaper which has a front-page article about the infected.
Inspect Joel's bedroom to find used tissues everywhere indicating his single man's life and... Well, actually not, he cleaned them up of course. Looks like the city's in big trouble according to the journal.
Head downstairs after this and check the ringing cellphone in the kitchen; Uncle Tommy again. Looks like dad left a note on the fridge saying he's home late. Well, life happens, right? Maybe he's in his working room on the other side of the house? Indeed, a long scene triggers soon after you enter. While you're in the car you can look around and zoom in by pressing L1.
When you're required to do so, press square multiple times to get out of the car. After this, run down the street while staying close to Tommy. Do not wander too far off or you'll be instantly killed. Should you get grabbed by one of the Runners walking in the street, you'll have a chance of pushing them away.
Follow the street and head around the right corner; move past the fire truck and go into the alley on the right side of the street when Tommy tells you to.
Push away the Runner and follow Tommy through the back alleys. Quickly head inside the restaurant, then move to the far end of the hill to conclude the prologue.