Before you buy the fabric...

The best way to avoid wadders (failed projects), UFO's (Unfinished objects) and semi-wadders (partial waste) is with a well-planned project.  Ask me how I know...

Seriously. (*wipes tears from eyes)

Below, are some examples of sketches from books I own, and I have found useful for planning and articulating  2-d versions of things I've created over the years...

Details, and how to draw them - I've probably ben using this book for 25 years now...

A good place to start for sketching a posed fashion body - I've made several body type variations using this sketch...

Before you sew... 

Instructions and illustrations to hep you communicate and create - from Draping for Fashion Design by Hilde Jaffe and Nurie Rellis (used for an FIT Draping class in the 80's)

There's an idea.  You may need to convey that idea to others, to the intended wearer, or even yourself.  Focusing in on the steps you take to make an idea a PLAN is a great way to start, but I will tell you that sketching is very difficult for me. Sketching and/or conceiving using the computer doesn't translate well to the real world for me. What this means, is that I spend a lot of time working in 3 dimensions, when I know I might be better able to solve design problems faster by really sketching out the solution/plan of action earlier in the game.

From Costume 1066-1966 - purchased at the Tate Museum in London, ca. 1983 or so...

The pamphlet I scanned (top) is full of tools to help a designer articulate what he/she is trying to create before any actual construction, pattern making or draping begins. I have been using this book since my first classes at FIT, and it is still amazingly useful. (And it only cost $1.75 when I bought it WAAAAY back then - and it there's no copyright.)

From Erte's Fashion Design Illustrations - Harper's Bazaar 1918-1932

Can you still find resources like these in the garment district? Yes, and places beyond...

Fashion Design Bookstore
FIT classes (particularly continuing education classes)
Around the World Magazines
Ebay
Mood Fabrics (figures to use for sketching)

Some people are better at planning than others, and some are less patient when it comes to the actual hands-on aspect of the process.  I am squarely in the latter category, but, I must say, that it does cost me time and money to skip steps.  I encourage you to learn from my mistakes!