Hello, I am relatively new (just started about 1 year ago) to the modeling world and would like some tips on how to improve. Below is a picture of my first two car models I have built. I simply bought the kit, paints, and built it as is with no skills or help from anyone, only using the instructions to guide me. I simply want to perfect my skills by getting some help and tips from people who know what they are actually doing. If anyone can provide any advice, feel free to let me know.
Thank you.

Few more shots perhaps?

The Ferrari looks fairly clean.
What did you use to glue the headlights on the Ferrari?

Superglue tends to fog and regular cement can mar the clear plastic.

A good alterative to both is either white glue (Elmers) or Krystal Klear (most hobby shops should have this) -- which is essentially fancy white glue from what I can tell, but it works incredibly well on all clear parts.

A few more shots, would be a good idea

Hey Glen, welcome aboard 1st off.
As for you builds, like others I'd have to say let's see some more pics of those two cars for a better analsys.
Did you superglue the Ferrari headlight covers on? I've used the gold lable CA with good results...meaning no white fog. It's the "foam safe" stuff and while it's strength is less than the usual types, it doesn't give you any fog{vapor etching} on any glass that you may use it on. Plain old white glue works great for attaching glass too.
Looking at the Ferrari, I don't see any panel line wash...this kind of a wash is a really diluted black that you run into the door, trunk and other body lines to bring out those details. About 70-60% thinner to 30-40% paint is the consist of a wash that gets brushed in with a fine tip - you let it run into the cracks. The same kind of wash would be used on your mustang's grill to give it depth.
So, are these your 1st models or is this just your 1st venture into cars{meaning you've built other types...plane/boat/figures/sci-fi...?}
Did you use rattle cans to paint the cars or do you have an AB{air brush}?