Page structure

The lead section: WP:LEAD, with the lead sentence, WP:BEGIN
The table of contents WP:TOC, mostly auto generated
The body of the text, with sections and perhaps subsections - WP:BODY
Images etc. -> Wikimedia Commons. Embedding files from commons: Wikipedia:Wikimedia Commons. Go to commons: c:Main Page
Appendix, with references and external links - WP:APPENDIX
Footer with categories - H:CAT

Editing

See: Help:Editing for an explanation on how to edit and save.
See the WP:CHEATSHEET and Help:Wiki markup for more information on the wikicode.
Wikipedia is about links - internal links and external links. WP:LINKS; internal links: not to little, not to much; external links: always in a separate section at the bottom (or in references).
Work through the tutorial, or get some practice in your own sandbox, to get used to the elementary syntax. And often look at other pages, to see how experienced Wikipedians have done things.

Make a list of pages that you find useful; on your user page or a subpage. For instance: try to make a link to this page (then it's no longer a poor little orphan). You can also make a short list of pages that are related to your field of study. Make a list of useful literature.
Templates: for instance: infobox
Citations and referencing: Help:Introduction_to_referencing/1
For citations you can use Template:Cite book or Template:Cite journal or Template:Citation or Template:Cite web
if you're not in the Main namespace, please sign your posts!
redirects and disambiguation pages
Make a watchlist - WP:WATCH

There are lots of help-pages; a good start is the help button in the left column.
Don't hesitate to ask advice from experienced editors; use their talk pages. You can also visit the Teahouse.
The Manual of Style: WP:MoS; and a nice Beginners' guide to MoS.

the text below temporarily copied from Dutch page of project / integrate this in the "final version" of the text

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