1. Ingredients are always listed in order of quantity, so the ones at the top of the list will always be most prominent in the formula. This is often where ingredients like surfactants (foaming agents) come into play or the percentage of water comes to light. If you're trying to avoid certain ingredients, then make sure they're not in the top 50% of the ingredient list; any lower down and their concentration is so limited it may not actually make a difference.
2. Ingredients lists must conform to the INCI (International Nomenclature of Cosmetic Ingredients) standards of identification, a system of names for ingredients in cosmetics that is based on their scientific origin (i.e. Latin!) However, many companies want you to understand their ingredient list and will put both the INCI name and the commonly recognised name on the bottle in brackets, i.e. Citrus Aurantium Dulcis (Orange) Peel Oil.
3. Preservatives are present in non-organic products as they help to keep the formula fresh. Ingredients such as Formaldehyde, Salicylic acid, Benzoic acid and Calcium Benzoate are simply present to keep the other ingredients stable and performing as they should be. However, they can cause irritation if you're extra sensitive, so it's worth familiarising yourself with these names and doing your research on ones to avoid.
4. Organic ingredients are often marked with a star after them (*) for clarity. If a brand is claiming to be organic, or simply infers their 'natural' roots through product names or branding, then it's definitely worth having a look and seeing how much of the ingredient list is 'starred'.
5. If that revolutionary active ingredient that claims to change the world is lingering by the bottom, then it's probably not in a high enough concentration to really do anything at all. The majority of formulas will be made up of water, surfactants, lubricants, emollients and other 'bases', so the level of active ingredients can be incredibly low. A lot of ingredients will be included just for a point of different or to provide a marketing story to sell the product; be wary!
6. Ecocert are a body that provide a 'stamp of approval' to brands that use organic ingredients. However, this can be as little as 10% of the overall formula so it's to be taken with a pinch of salt. Their little stamp often appears next to one from The Soil Association (the UK's independent organic body that campaigns for healthy, humane and sustainable farming,) which brands like to add for credibility when claiming to be clean. These are ones to watch out for, but they don't mean that the product is completely organic or as pure as a home-grown carrot.
7. The individual ingredients that make up a fragrance or flavour don't have to be disclosed due to privacy laws, only the addition of a fragrance or oil. These are classified as 'trade secrets' so the brand has to make no disclosure as to what individual components make up the taste or smell, only comply to legal classifications and include approved ingredients.
I hope this helped a little! Do the backs of bottles in your bathroom confuse you, or are you wised up to the tricks of the trade?