Question1. What do you mean by conversion? Do you mean getting someone to answer simplest call to action such as "read more here" or actually selling a product or service?

What you're talking about here are two different ways to measure your website. "Read More Here" is what I would call a variable affecting your conversion rate. I call these kinds of variables "Micro Conversions" because they are all small (microscopic even) steps toward a full conversion. A micro conversion is something that you should test and measure. "Read More Here" might get a worse click-through rate than "Click here to find out how to win a month's supply of vintage wine." So by improving this click through, you get person browsing to take another small step toward your final website goal. By doing this, you improve your overall conversion rate, which in this case is to get someone to register or subscribe to win a month's supply of vintage wine. Micro conversions can be tracked by measuring click through of links, or read time for content, or bounce rate for headlines and copy. Full conversion is persuading your visitors to do what you want them to do. In my example, it would be registering to win wine, but it could be subscribe to a newsletter, download an audio file, buy a product, sell a service or whatever, but it should reflect what your website's business objective is.

Question2. What strategies would you suggest when there is no "online" conversion possible? I need them to call me for more info, to learn more and to eventually give them a proposal.

There is no such thing as "no online conversion". You're looking for leads who will eventually phone you but visitor is one with power. If you don't give your visitors a reason to let you continue to have a dialog with them, then they won't. Using opt-in is one answer. If, for instance, you ask for a name, email address and telephone number from your visitor so that he can then get useful information from you in form of a free report or audio file, you do two things. First, you qualify visitor as someone who is interested in your services, and second, you get permission to contact him/her again. You need to build into your website a powerful reason for your visitors to give you permission to email or talk to them rather than expect someone to pick up phone. In your case, you say they need to ring you to learn more. Put what they need to learn into some form that they can opt in to get, such as a white paper, report or audio file. Then you have a conversion rate that is percentage of people who give you permission to continue dialog with them by giving you their email address or phone number so that they can learn more about your offering. People visit a website to get information, so give them means to get it.

Question3. What if product you sell is also sold by several others on other websites? How do you get someone who is browsing Internet to notice your site and want to order from you?

In offline marketing, a successful tactic is differentiation. It's no different online. If you stand out from your competition, then you get noticed. What makes you different (not necessarily better, just different) from your competition? A USP makes an enormous difference to conversion rates. We improved subscriptions by 11% per month for six months by differentiating ourselves. The second point is that your site should be of use to your visitor. The one thing that all people online have in common is that when they browse they are looking for information. So give your visitors what they want in form of education. If your potential customers become educated about your offer and take away something useful from your website, they will remember you over your competition.