Don't hit every car you see
Yes, I know, there is immense satisfaction to bumping into other cars and destroying everything in your path. But hold on there, tiger, it's not as simple as you think. You can't just smack everything in your way freely. By doing that, you slow your speed down, which you want to try and avoid.
You can smash cars but you must find a balance. Try to pick up some speed by avoiding them. From there, you'll be wound up, and then you can crush cars like a pop can. But again, it's all about finding that balance. On occasion, you'll get "Road Rage" will allows you to destroy in amazing fashion.
Getting this also picks your speed up a bit too. It doesn't last too long, but the effects are really cool. Hitting other cars is a big part of the fun in Speed Demons. Just try to be smart about when to do so.
Use your power
Certain challenges allow you to use a power to destroy other vehicles. Initially, you'll use a laser type of power that you can pew pew away. This is a great way to get some takedowns and blast traffic out your way. You can use it frequently. Of course, you have to be behind other cars in order to strike with the attack.
Knocking out opponents will rack up your score. Plus, it's just a lot of fun to do. The challenges that involve destruction definitely make you reminisce of the Burnout days. Use the powers, cause mayhem, and have some fun.
Try and stay as close to the middle of the road as possible
One of the trickier things about Speed Demons is that the roads are pretty narrow. It's certainly nice to have the challenge but that means paying attention to your surroundings. On most occasions, the right side will have a cliff where you can fall off into an oblivion of water.
And when you're racing, there are times where opponents may try to knock you into the deep blue. So definitely be aware when heading to the right side of the track. Be careful of the left side too, because there are times where it may slow you down by going too far.
Lastly, on some tracks, even the middle (*gasp*) can be your enemy. Some tracks have the dividers and street lights that are in the way. So when going down the middle, you may crash into them, which of course can screw you up. In short, pay attention to your surroundings as you weave through everything.