This has been a stumbling block for me for many years and I still don't think I have it right!
Even determining the difference from wholesale and retail I struggle with!
I know that everyone has a different way of doing things and it would be great to see some of peoples tips and people can determine which is the best way for them.

Try this: http://www.businesslink.gov.uk/bdotg/action/layer?topicId=1073899859
But here's my ROUGH guideline for a quick reckoner
TRADE PRICE = cost of materials + (hours spent on the piece x hourly rate)
RETAIL PRICE = Trade price + margin(%)
e.g. a ring, materials cost £80 (including gas, studio rent etc), took 3 hours to make at an hourly rate of £25
trade price = 80 + (3 x 25) = £155
retail price = £155 + 30% = £201.50
You set your own margin (set it high enough so you can discount and still make a profit) and your own hourly rate (set it high enough so you can make a living without having to work all the hours god sends, and so you can offer discount to repeat trade customers).
Good rule of thumb: your hourly rate should be your ideal annual salary divided by 1000 hours, so £35,000 pa = £35 per hour. Why 1000? Because a calendar year = 1000 working hours give or take.
You can work out your hourly rate more scientifically than that, and would have to if doing a business plan (rent/mortgage, loans, gas, electricity, petrol, council tax etc)
But the formula above separates your business costs from your living costs. Don't forget to include studio rent and power etc in the business cost, as well as tools, storage of materials, insurance etc. You can break that down hourly as well across 1000 hours.
The other even easier but less scientific way to set your price is to look at what similar things sell for and price accordingly. Ask a friendly retailer what their margin is and that will get you to the trade price.
i.e. if a necklace is selling for £150 and their margin is 40%, the trade price was (150/1.40) = £107
But remember: your price must a) cover the cost of the materials and b) cover your cost of living and c) have enough padding that it won't matter if the piece takes time to sell. c is important - it's called cash flow...
Selling for less than that = a loss. Never price your work so cheaply you can't make a living off it.