The best thing you can do is 1- Buy your tickets the night before - but get a map and 2- Get there before it opens. If you do these two things, you'll get to see most of the best attractions without waiting in the line for too long. If you do not, you can still see a few good rides, but you will spend most of your time waiting.
The most impressive rides to see and the ones that are "classic" Disneyland are these:
Indiana Jones Adventure
Pirates of the Caribbean
The Haunted Mansion
It's a Small World
Big Thunder Mountain
Since you are going in summer, and the crowds will be heavy, the opening time is 8:00am , but get to the front gate by about 7:30am.
Let me suggest a pattern to follow so that you see the most you can. Here we go! :)
Walk right down Main Street and take an immediate left into Adventureland. Keep walking until you reach the Indiana Jones Adventure. This is Disneyland's premier ride (and one of my favorites), and if you like the movies, you'll love this! It's a runaway jeep ride. Regardless of the line length, if you go first thing in the morning, go here first.
Once you get off the ride, you can do one of a couple of things if you want to ride it again: 1-Go to the entrance and find the attendant. Tell them you are "single riders". You'll get to go to the front of the line but you will not be able to ride together. They will use you to fill in jeeps with empty seats. 2- Or go to the "Fastpass" Machine. Fastpass lets you put in your admission ticket, and the machine spits out a special ticket with a time stamped on it. (Make sure you take out your admission ticket and keep it with you.) When your designated time arrives, take your ticket to the Fastpass line. You'll get to walk by most of the crowd. This is important. You need one Fastpass ticket for each person. You have a one hour timeframe to return or your Fastpass is not valid. (By the way, after your return time begins, you can get another Fastpass for any other ride that offers it.)
If you do not go to Disneyland early, go ride to this ride anyway and use one of the two ideas above to make sure you get a ride on Indiana Jones Adventure.
Walking out of Indiana Jones, turn left and walk past Pirates of The Caribbean and the Haunted Mansion right to Critter Country and go to Splash Mountain. This ride will have very long lines all day as well. This is a water ride with lots of Disney characters. You will get wet, but it is so much fun! If you want to ride this again, go back in line if it is short or use Fastpass again.
After riding Splash Mountain, go back the way you came in and ride The Haunted Mansion in New Orleans Square. It's not scary but suspenseful and the special effects are amazing.
From there, go back to Pirates of the Caribbean. If you walk to the Treehouse, you've gone too far. This is my favorite Disney ride and one of the best. Captain Jack Sparrow robots are very lifelike- and he makes an appearance three times in the ride. Pirates is a ride where the line moves pretty fast, so even on the very busy days, the wait should be no more than 30-40 minutes.
Let me say that at this point, the crowds will start coming in. Depending on how early you are there, you may get on more rides than this before the crowds. Also, make sure you walk around and explore the shops and restaurants as well. But rides are the most important and why Disneyland is famous! :)
OK- Walk out of Pirates, make a right turn and head across the park to Big Thunder Mountain in Frontierland. This is a Disney roller coaster. It's not the biggest or scariest one ever, but it is very fun. If you can, ride it at nighttime, too. It's like a totally different ride. This is also a ride that uses Fastpass, by the way.
Probably by now, I am sure the crowds are there, so be prepared to wait in line!
Leave Big Thunder by taking a left and walk through the Frontierland fort across the park to Tomorrowland. You are headed to Space Mountain.
This is a roller coaster ride through outer space. It is also a Fastpass ride. It will have a very long line, so if you can get a Fastpass, it might be smart to do it. If you do, from there I would either go to Buzz Lightyear AstroBlasters . It is a video game ride where you shoot targets as you ride along a track. (It has Fastpass as well.) Or if that is not interesting to you, consider going to see the 3D movie, Captain Eo starring Michael Jackson.
If neither of these options look good, then head toward Fantasyland (through the Castle) all the way back to It's a Small World. This is a very sweet musical boat ride around the world. People love it or hate it (we love it!), but it has the feel and "stamp" of Walt Disney all over it.
OK- If you've done these, you have ridden the best in the park, but there are many more little gems to be found all over.
And make sure to check out when the fireworks show is!
Here are my suggestions for other Disneyland rides worth a look:
Matterhorn Bobsleds : a coaster ride through the Swiss Mountain
Tom Sawyer Island: an outdoor island to explore caves etc.
Mark Twain Riverboat: a relaxing boat ride around the river
Peter Pan's Flight: In Fantasyland, a ride over the rooftops of London to Neverland
Jungle Cruise: In Adventureland, a silly boat ride through tropical rivers with (fake) animals. One of the first rides in 1955.
Roger Rabbit's Cartoon Spin: a ride through the world of the movie. The lines are long, so use Fastpass if you can.
Disneyland Railroad: A train ride all around the park. Ride it all the way back to where you started. You can get on it at Main Street, New Orleans Square, Toontown or Tomorrowland.
Half the fun of Disneyland is walking around and exploring things.
Wish I could meet you there and take you around personally!