I think it is best to be clear in what you speak. Record any practice attempts you make. Listen to it. Send it to some experts here and ask them to judge on what the mistake is. Often, people from the same country like friends and all have same speaking habits and cant judge properly.
Furthermore, take all notes while the retell lecture and other stuffs.
For the read out loud, be clear and confident. Speak with enthusiasm.
For the describe image, I followed my rule for giving out the following information only and it worked.
**Topic – 1 sentence on the topic. Make sure you paraphrase the topic and dont just say it as it is.
**Trend/axes – Say ” the x axis of the graph shows so and so and ranges from so and so while the y axis denotes so and so ranging from so and so.
**High – Speak about the highest value on the graph
** Low- Speak about the lowest
** Conclusion – Say a sentence on the conclusion if time is enough or else leave it.
This should do the trick. IT did for me.
Cheers and best of luck.