My first experience that I had was that people couldn't tell what word bubble to read first. Make sure to try to place things in a good way to show which way to read them all, otherwise, it could become confusing to readers.
Font is always something to make sure you experiment with since that could also determine if people can even read the comic....
I also suggest planning out the set up of the pages before sketching out characters. (How do you want the page to flow? Your boxes don't ALWAYS have to be just straight squares in a row. Sometimes, you can make characters and actions pop more by changing the shape or having the character not be confined by the boxes.)