Know-How Exchange : Strategy

I would start by buying and reading the The Small Business Start Up Kit, by Peri Pakroo. Covers the mechanics of starting a business, which may also help guide you in choosing what business to start.
https://expandabroad.blogspot.com/2005/08/start-up-book-recommendation.html

I think you should probably sell something that will make petrol more efficient. take a look at (my green oil). not sure about the website. this will sell since oil prices is being a bitch.

You should start something that will empassion you-- put a fire in your belly so you'll jump out of bed in the morning. Then, develop your business plan. There are many ideas out there that sound good on paper-- but without planning and really reseraching the business-- you find you have something that is a "me too" product or not saleable.

Don't get caught in the green trap. Green is a feature not a benefit. I dare say that every manufacturer of furnishings is "green" in some way. I just joined the ASTM new committee on sustainability. Finally-- a REAL standard that will define green. I am very glad to be a part of it at this ground floor committee.

Sell Well and Prosper tm

Sell something that you're an expert on, not something that you can sell. Why people will purchase from you isn't because of your selection (unless you've got something unique) - it's for the information you're able to impart about the product based on your deep knowledge and opinions.