I have got 6 bands in IELTS with no band less than 5.5. What are my chances to get student visa for New Zealand?

You may be given:
Bar charts, Line graphs, Pie charts, Tables, Diagrams, Maps, Process descriptions

You should write at least 150 words for Writing Task 1, but the ideal word count ranges between 160 and 180. Writing less than 150 words will result in a penalty.

Ideally, the report should comprise a Summary of the 3-Step Approach.
Introduction: Paraphrase the question.
Overview: Highlight the dominating feature. 
Specific Details: Explain critical data with specific figures or comparisons in 2 body paragraphs.

Start by looking at which context you can use the words in. You can establish associations between new words and familiar concepts. To aid memorisation, practice actively by using the words in daily life.

The speaking test lasts around 11-14 minutes. The test includes 3 parts - Introduction & Interview (Part 1); Cue cards (Part 2); Follow-up discussion (Part 3).