What promotion (from the marketing mix) is the best for an investment product/service?

Answer 1

the most important aspect of an investment product/service is money, hard-earned customer's money. so you need to gain trust with the customer.
the best promotional tool for such a product would be "Word of Mouth". this is the BEST tool for any product. A satisfied customer would always act as your brand ambassador and would publicise your product/service to his family & friends. This will bring in more customers for you and the trust levels would go up.

Answer 2

Here’s a few time-honored ways of website promotion:

Links

Getting/buying links from other well established sites in you niche is always a good way to get traffic. These links are NOT necessarily for search engine ranking, you’re looking for good prominent links that people will actually see and click on. This may be a homepage link exchange, or if your budget allows try buying one-way links.

Sites like “text ad links” offers some decent value here, but it
may just be better to search out sites within your niche and contact them directly.

...Just don’t send out a form letter, do some research on the site and contact them with a personalized note.

Article Syndication

Write articles about your niche (or have them ghostwritten) and submit them to the big article directories – in the resource box, include a little about yourself and a link back to your site.

Better Yet – contact others in your niche and offer to give them an article in exchange for link backs. If your articles are well-written and insightful, this should be an easy sell, most of us are always looking for fresh content. If your article is good, site readers will often click through to have a look at your site.

Good Luck,

Dave
http://www.affiliateprofitcenter.com