Be on time and be PREPARED. Forgetting the required paperwork will delay your interview.
Dress appropriately.
Be patient.
Seek community and legal support in advance so you are not surprised.
Except under certain extenuating circumstances you must be able to read, write, and speak minimally (proficient, passable) English to be eligible for naturalization. Prepare in advance. There are many community resources to support language acquisition. The BCIS is sincere in their efforts to ensure new citizens understand basic American civics and history, but that does not mean it is easy.