Phrasal verbs are definitely a huge help. I've noticed there are a few other spots in a sentence where I know a writer doesn't have English as their first language when I see them. I worked as an English tutor in college and these days do a lot of ghost writing and proofreading for my employer who is a native Spanish speaker. These things come up constantly.
A vs AN:
Basics - singular don't forget to use yours a's and an's.
Advanced - it's actually the sound that matters, not the letter the word starts with. "An honest" sounds like "an onest" "A european" sounds "a yuropean"
Pay attention to the number of things one is talking about at all times.
For example, the noun the verb "is" belongs to here was "number", not "things" = singular = "is".
"You" always uses same verb word as "we and they". All use are, were, and have, and never have an S at the end of other verbs (swim/swims, hate/hates). I is the same way, but for "I am" instead of "I are".
I've noticed that the letters ED are sometimes the first to go in a sentence, especially if it's harder to hear out loud. I've corrected the following a lot:
What happen was >> What happened was
After, we decide to >> After, we decided to
We really tried. We even allow her >> We really tried. We even allowed her
Note: I really try to avoid most formal language terms when explaining this. I found a lot of my students' eyes would glaze over when I did. If they didn't, I was preaching to the choir, so what was the point?