Reddit reviews Writing Software Documentation: A Task-Oriented Approach (Part of the Allyn & Bacon Series in Technical Communication) (2nd Edition)

Books:

Writing Software Documentation. It's an oldie, but a goodie. Great text to help with learning the basic concepts behind tech writing (task orientation, audience analysis, etc).

Business and Administrative Communication. Super expensive, but, imho, one of the most solid all-around books about writing in the business world. It covers everything from memos and effective PowerPoint presentations to RFPs and Feasibility Studies, and it does it extremely well. This was one of my college textbooks that was so useful that I kept it, and when the HR department "borrowed" it and "forgot" to give it back, I bought it again.

I remember The Handbook of Technical Writing being a good base, too. That was the text for my intro to technical writing class. Covers usability studies and other fun things.

A style guide of your choosing. If you want to write for software, though, get the Microsoft Manual of Style. Otherwise, Chicago or AP.

Software:

Download a trial version of RoboHelp and play with their sample projects, and learn how to use it. After you do that, try the same for madcap Flare. FrameMaker is important to some technical writers, but I've never had a job that didn't phase it out way before I started working there. It feels like one of those products that is slowly dying but just won't let go (but, then again, RoboHelp felt that way in 2007, so I am probably wrong about that one!). FrameMaker is primarily used for publishing layouts and such. If you work in hardware you might see it more often. Software generally doesn't ship with printed guides these days, though...

Learn to use MSWord like a pro. Specifically, learn to use styles, the reference tools, automatic TOCs, indexes, review, the developer's tab, and pretty much everything that is on the MS Word certification exam. Secondary to that, make sure you understand Excel and all the other office tools fairly well.

Learn a CMS, like SharePoint.

Personal:

Get used to criticism. Everyone thinks that their writing is better than anyone else's, and everyone has ideas. People will pull your writing in fifty directions every day.

Extinguish passive voice. Forever. Kill it dead.

Use fewer words and send your adjectives on vacation. Simple and sweet.

Be awesome at figuring things out on your own.

Visit a whole bunch of help and documentation for various products and geek out on it. Study the good and bad, the effective and not, the appealing and the ugly. Keep notes about what you like and want to emulate and what you hate and don't find helpful.

Practice:

Take your new skills and use them. Find a good open source project and volunteer some time writing up some documentation. Some potential projects are tiki.org, Mozilla, etc.

Fun:

Read all of the Tina the Tech Writer strips from Dilbert. That will be your new life. :)