If you're starting out in writing, editing or marketing communication, it would be helpful for you to know where to go to check spellings, word usage, grammar, style and punctuation.
Why? Several reasons. Mainly: your aim is to get your message across, and introducing errors can cause misunderstandings. It can also distract your reader if they notice the error (and forget what you're trying to say). Another reason is that if you'd like to be taken seriously as a business or professional organisation, poor English can say otherwise.
So to help you communicate well, here are some of the standard reference guides used widely across the editing profession.
In Australia, the go-to resource for spelling and word meanings is the Macquarie Dictionary. This is now published online and accessed via subscription (check if your local library has a subscription for its members). The hardback 6th Edition currently costs AUD99.99 on Macquarie's online shop.
The standard style guide here is the Style Manual for Authors, Editors and Printers (6th edition, John Wiley & Sons, 2002). Work is currently underway on a long-overdue digital 7th edition, but meanwhile, turn to the Style Manual to check conventions in titles, capitalisation, punctuation, numbering, use of italics, and a million other perplexing practices. Do you or don't you capitalise each entry in a bulleted list? See the Style Manual (pages 142-3).
Language being the ever-changing beast that it is, it's worth checking that, once you've chosen your words, you're using them correctly. This is where usage guides are handy. My favourites are Modern Australian Usage by Nicholas Hudson (3rd edition, Allen & Unwin, 2015) and Pam Peters' The Cambridge Guide to Australian English Usage (2nd edition, Cambridge University Press, 2007).
New editors in Australia regularly turn to Janet Mackenzie's The Editor's Companion (2nd edition, Cambridge University Press, 2011) for help with editorial processes and working as an editor. I also like The Australian Editing Handbook (3rd edition, John Wiley & Sons, 2014) by Elizabeth Flann, Beryl Hill and Lan Wang.
I hope you find these as helpful as I do in making messages matter!