Luckily i was in an AP Art class through highschool and won money for college for my artistic abilities. Came in second place in all of Virginia and missed winning $36,000 scholarship....but now im going to help you lol
Simplicity is key, we want to catch potential costumers and you don't want them straining to see what you are advertising. Find a comfortable font that has its own edge/personality(something sharp and clean), but not wingdings hahh
Color Scheme- take a look at sports teams and there logo colors. Find two or 3 colors that compliment each other
Logo- well if you have ever seen the Infinity car comercials, there is a simple little "3 line sketch" they use to show the outline of the cars. If you have an artist in your area and have a favorite car shape, let them draw you one up.
Of course, you already know this, make sure that phone number is Gigantic haha. I also found that some people are weird and dont like to call. Throw an email on there too if you want.
Overall, make the trailer look so professional that its ridiculous(not tacky of course lol). If you can make it look like a big deal, then people will want to know all about it