Don't apologize about your poor English.
The audience notice that you are not a native speaker as soon as you speak.
Communities of scientists and engineers are relatively tolerant to English spoken by non-native speakers.
An oral presentation is not for showing off your fluent English,
but for delivering the audience the information that you want to share with them accurately.
Don't read literally slides or notes instead of talking to the audience.
The audience can read slides by themselves without listening to your reading.
Because slides are information concisely,
you should elaborate the information to supplement slides with your own words.
Don't use rising intonation at the end of a statement unless you are asking a question to the audience.
Tone and intonation of your voice carry lots of information to listeners together with gestures.
The audience may be confused or misled by a wrong way of using them.
Don't switch slides back and forth frequently.
This behavior distracts the audience from listening to your talk.