Practice and rehearse key English phrases:

DO
establish a clear objective.
talk about what your audience expect you to talk about.
organize the information.
use notes or key words to assist.
have a strong openng and closing.
make interesting.
use your voice for effect.
keep it simple.
use visuals which improve impact and clarity.
handle equipment professionally.
speak with sufficient volume and intonation.
use summaries to link the parts.
think about the  cultural environment.
dress for the occasion.
prepare and practice beforehand.
be confident and relaxed.
balance spontaneity and preparation.
handle questions positively.

DON'T

make assumptions about the location and facilities -check beforehand.
present information which is too complex for the audience.
talk for too long.
tell irrelevant anecdotes or inappropriate jokes.
speak too quickly.
use too many visuals.
photocopy small text onto an overhead.
read from scripted text or visuals.
block your audience's view of a visual.
talk with your back to the audience.
use distracting mannerisms.
forget to summarize at the end.