There are pages posted on the site that will give those wanting to learn Temari good starting points -  to make it easier to zero in on these, a summary list is offered here.

Basic Stitches - diagram of use of herringbone stitch for basic stitches in Temari
Angle Templates - templates to use to check or mark polar angles
Chrysanthemum Photo Tutorial - step by step on working this stitch
C10 Division Photo Tutorial -   step by step working this division
Frequently Asked Questions - you asked
Getting Started - essay on the basics of what you need, etc. 
Beginner Patterns - suggestions of what patterns work best for beginners (and why)
Squares and Rose Garden Stitch Diagrams - basic diagrams of these stitch elements
Glossary - run down of terminology
Watch a Temari be Made - Photo Essay - overview of working a Temari

Look for a Temari Teacher
Learn with an Email Mentor
Temari Books in English

And - collected thoughts for beginners from the discussion group:

From Pat W - I have noticed that many of you have trouble starting out... and my very best advice to you is to start out doing a very simple design, on a 2.5 inch (or similar) ball. Forget doing anything more than a simple 4 division (squares, spindles, interwoven squares, hexagons, stars, wrapped bands, etc.) for your first 5-6 balls, and you will find that you are doing more and having more fun with them, and not getting frustrated at trying to do something you're not ready for. I keep my students on simple divisions (4-24 parts) for the first year. they are building their skills. There are dozens of lovely designs to do, and when you are used to doing multiples the complex divisions will be relatively easy.... and then the sky is the limit!!!

From Sue H. - I don't think enough can be said regarding using a fine grade of yarn, like Baby, fingering, or machine yarn, and keeping the ball moving in ALL directions when wrapping. If you are finding it difficult keeping things round, start with a foam core.  Most are pretty round to start with, then add your layers of yarn, then thread. (I know some like to add batting before the yarn layer, but it is totally optional!... skip it if you're having "round" problems.)  If you find your finished ball is not "on-round", then it is definitely the way you are wrapping.  Being slightly off is normal... and unless you are doing an all-over pattern that fills in the entire ball, it will not usually be that noticeable.