The spots being revealed in this post are Doc's house (1985), the Burger King Marty skates by, Marty's house (1985) and Doc's house (1955).
In the very beginning of the first film we see Marty enter Doc's house in 1985. In this classic scene, he hooks up his guitar to the amp and completely blows the speaker to pieces! "Rock and roll." When Doc's thousand clocks go off Marty realizes he is late for school and heads out in a hurry. From there, he exits Doc's house and skates past a Burger King on his way towards school. We see him grabbing onto the back of several vehicles to speed up his trip.
After a long day of trying out with the Pinheads for the Battle of the Bands at school and an afternoon of making out with Jennifer, Marty heads home. We see him skate off while Huey Lewis and the News play Power of Love. As he gets to his street we see the Lyon Estates signs for the first time. This is the name of Marty's neighborhood and will be shown again several times in the trilogy.
Marty skates up to his house to find his father's car being towed into the driveway. As he heads into the house, George McFly is being verbally accosted by the Hall of Fame douchebag Biff Tannen. But of course George takes it because after all, he's "not very good at confrontation."
Fast forward to later in the film when Marty goes back to 1955, he gets hit by his grandfather in the middle of the street (I will reveal this spot later), and he seeks out the only man who could help him, Doctor Emmett Brown. After Marty finds the property which he discovered in the phone book, we see him running up the path to the house. Doc answers the door wearing that strange psychic device on his head and can't believe that "future boy" is visiting him from 1985.
Before getting into the precise addresses of each of these spots, I just wanted to mention that BTTF did a great job of blending each location together. And as casual viewers it never becomes evident to us that one scene is filmed in one location and another scene is filmed in a location 50 miles up the road. Southern California is the filming mecca for a reason. Great locations are fairly close and it isn't a huge ordeal if a movie is being filmed up the street. When movies are filmed in places like Arkansas or Ohio the entire town would show up drinking their morning coffee trying to get a glimpse of the star. In Southern California it becomes normal in some places to drive down the street and see flim crews.
Now that that's out of the way, let's look at these particular filming spots. Marty visits Doc's house in 1985 before school. He hears the clocks go off, talks to Doc on the phone and skates out in a hurry. He skates past a Burger King on his way to school. This is in Burbank, California. Doc's house was actually a facade built for the movie. There are no remnants of this building today but the Burger King is still going strong. Marty skates to school through the Universal Studios backlot and onto Hill Valley High Schoolwhich is actually Whittier High School. After school he meets up with Jennifer and skates home. His street and home are located in the Arleta area of Los Angeles. When Marty looks up the 1955 Doc and visits his house, he is visiting the famous Gamble House in Pasadena, California.
So now you can start to see how many different locations it actually took to create this fictional town of Hill Valley. The exact locations can be seen below.
Doc's 1985 house and the Burger King are located at:
535 N. Victory Blvd
The Lyon Estates street markers were located at:
The corner of Sandusky and Kagel Canyon Street
Los Angeles, CA
Marty's house is located at:
9303 Roslyndale Ave
Los Angeles, CA
Doc's 1955 house aka The Gamble House is located at:
4 Westmoreland Place
**Again, be respectful when driving by someone's home. Also, Arleta isn't the best of areas so I would only recommend visiting this spot during the day.