I usually start with my logo and a rough color pallet. For the most part I like to keep it simple and let the products shine through, especially when I am doing a clear packaging so you can see the product without too much distraction. An exception are my bar soap labels which are a little fancier since I mostly use recycled paper boxes that hide the soap.
Here is the new square label for the Cardamom Vanilla Marshmallow Cream Soap! (And the old for comparison.) I added some more color to it as you can see - I am on a teal thing lately! All of the information is much larger and clearer. These didn't take too long since I had the old label to work from but my new lip balm labels for instance took 2+ hours to design! Usually the first label in a series of products takes the longest, then it is just a matter of changing color and tweaking text.

new
old
The ingredients and my company info will go on a smaller label on the backside. Soap labeling must have the company name, the word "soap", and the weight on the front. The company address can go on the back and I always include my ingredient list.You may have purchased soap that did not have ingredients and this is perfectly legal but I like to include it so my customers know exactly what the are purchasing. The rule is only for soap - I won't get into the details, but as soon as you say that your soap is good for anything other than cleaning, like that it is moisturizing for instance, it is then considered a cosmetic and must be labeled differently. A lot of my soap falls under this category. The FDA defines soap as:
- the bulk of the nonvolatile matter in the product consists of an alkali salt of fatty acids and the product's detergent properties are due to the alkali-fatty acid compounds, and
- the product is labeled, sold, and represented solely as soap
The 2 hour lip balm label! I'm slow! :)